- Email: [email protected]
Development of a short version of the Neck Pain and Disability Scale
European Journal of Pain 14 (2010) 864.e1–864.e7
Contents lists available at ScienceDirect
European Journal of Pain journal homepage: www.EuropeanJournalPain.com
Development of a short version of the Neck Pain and Disability Scale Eva Blozik a,b,*, Michael M. Kochen a, Christoph Herrmann-Lingen c, Martin Scherer a,b a
Department of General Practice and Family Medicine, University of Göttingen, Humboldtallee 38, 37073 Göttingen, Germany Institute of Social Medicine, Universitätsklinikum Schleswig-Holstein, Beckergrube 43-47, 23552 Lübeck, Germany c Department of Psychosomatic Medicine and Psychotherapy, University of Göttingen, von-Siebold-Str. 5, 37075 Göttingen, Germany b
a r t i c l e
i n f o
Article history: Received 8 July 2009 Received in revised form 1 December 2009 Accepted 13 December 2009 Available online 21 January 2010 Keywords: Neck pain Pain measurement Psychometrics Questionnaire Pain assessment
a b s t r a c t Previous evaluations of the 20-item Neck Pain and Disability Scale (NPAD) were indicative of excessive redundancy of the measure. The aim of this study was to develop a shortened version of the NPAD (sf-NPAD) based on results of item-to-total-score correlations and factor analysis as published by the developers of the original NPAD. Two items with the highest item-to-total score correlation were selected per factor subscale with the exception of one factor consisting of only one item. This resulted in the selection of 9 items for the sf-NPAD. The sf-NPAD was validated in a separate sample of 448 neck pain patients from 15 general practices in the area of Göttingen/Germany. Participants completed the 20-item NPAD German version and gave additional sociodemographic and clinical information. Psychometric properties of the sf-NPAD were evaluated using Cronbach’s alpha, item-to-total-score correlation, and unrestricted principal factor analysis. Construct validity was evaluated by Pearson’s r with clinical characteristics. Discriminative validity was examined by comparing differences between subgroups stratified by psychosocial characteristics using t-tests for mean scores. Cronbach’s alpha of the sf-NPAD was 0.88. Item-to-total-scale correlations ranged between 0.628 and 0.815, and sf-NPAD items homogeneously loaded on a single factor. Correlation analysis showed high correlations with criterion variables. The sf-NPAD scores of patient subgroups were significantly different showing good discriminative validity. In conclusion, the sf-NPAD demonstrated good validity and internal consistency in this general practice setting. The abbreviated version may facilitate applicability of the scale in clinical and research settings. Ó 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.
1. Introduction The assessment of pain of the spine is important in evaluating treatment effects and patient outcomes (Deyo et al., 1994). Neck pain is a highly prevalent condition with about two thirds of the adult population affected at some time in their lives (Cote et al., 1998). There are 11 measurement scales validated for the use in neck pain patients (Resnick 2005).The most commonly used selfreport instruments are the Neck Disability Index (Vernon and Mior, 1991), the Copenhagen Neck Functional Disability Scale (Jordan et al. 1998), the Northwick Park Neck Pain Questionnaire (Leak et al., 1994), the Neck Pain and Disability Scale (Wheeler et al., 1999), and the Patient-Specific Functional Scale (Westaway et al., 1998). These scales are generally considered to be comparable in terms of their validity and reliability (Pietrobon et al., 2002;
* Corresponding author. Address: Department of General Practice and Family Medicine, University of Göttingen, Humboldtallee 38, 37073 Göttingen, Germany. Tel.: +49 451 799 2530; fax: +49 451 799 2522. E-mail address: [email protected] (E. Blozik).
Resnick, 2005). The choice of the appropriate instrument should therefore depend on the particular patient population, the specific application context, and the ease of use for the patient and ease of scoring for the clinician (Pietrobon et al., 2002; Resnick, 2005). Prior to the development of the Neck Pain and Disability Scale (NPAD), none of the existing instruments designed for the measurement of neck pain problems adequately assessed the multidimensional effects of neck pain (Resnick, 2005). The NPAD measures problems with neck movements, pain intensity, effects on emotion and cognition, and the level of interference with daily life activities. The NPAD has shown to be responsive to treatment (Bolton, 2004; Goolkasian et al., 2002), to correlate with the patient’s global assessment of outcome (Wlodyka-Demaille et al., 2004), and to have robust construct validity (Wlodyka-Demaille et al., 2002). It has been found easy to complete for patients and is simple to score (Wheeler et al., 1999). Originally developed in the USA, the NPAD was translated to various languages (e.g. Wlodyka-Demaille et al., 2001; Bicer et al., 2004; Cook et al., 2006; Agarwal et al., 2006; Mousavi et al., 2007) including a recently introduced German version (Scherer et al., 2008).
1090-3801/$36.00 Ó 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ejpain.2009.12.006
864.e2
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
However, results of previous research indicated that the NPAD may suffer from excessive redundancy. Cronbach‘s alpha values reported in these earlier studies were 0.93 (Wheeler et al., 1999; Goolkasian et al., 2002) and 0.94 (Lee et al., 2006; Kose et al., 2007; Monticone et al., 2008; Scherer et al., 2008), with values higher than 0.90 being indicative of excessive redundancy of the scale (Nunnally and Bernstein, 1994; Streiner and Norman, 1995; DeVellis, 2003). Furthermore, individual characteristics predicting course and prognosis of neck pain should be assessed in patients in addition to the neck problem itself leading to a considerable length of the overall questionnaire (Carroll et al., 2008). However, lengthy questionnaires are generally more vulnerable to missing values and refusal (Eaker et al., 1998). An abbreviated version of the NPAD would be easier to use for neck pain assessment in clinical processes and in neck pain-related research. It would likely increase its acceptability and applicability, e.g. in multidimensional questionnaires, and reduce respondent burden. The aim of this research was to develop a shortened version of the NPAD. 2. Methods 2.1. Study design This is a survey of patients from a primary care setting in Germany with at least one onset of neck pain between March 2005 and April 2006. The study was approved by the local research ethics committee. As part of a project on the quality of medical care in general practice (MedViP), a network of 104 general practices has been established (Wetzel et al., 2005). A convenience sample of 15 of these practices within a radius of 30 km around Göttingen, a medium-sized town in Germany, were selected for participation and provided anonymised electronic patient data (year of birth, sex, diagnosis). Patients were included in a list of potentially eligible persons if at least one consultation because of neck pain was documented in the electronic patient record during the study period. All general practitioners were asked to exclude patients from this list, if they had a neck pain consultation because of a new trauma due to an accident, an injury, or violence, were terminally ill, suffered from cancer, were in need of nursing care or had severe cognitive impairment. Additionally, patients seen by locums only, patients who had moved to a region outside of the study area or who were not able to speak German were excluded from the study. Participants received a comprehensive self-administered questionnaire covering socio-demographic information, anxiety, depression, social support, and neck pain. 2.2. Neck and Pain Disability Scale (NPAD) (Wheeler et al., 1999; Goolkasian et al., 2002) The NPAD is a 20-item measure that was specifically developed for patients with neck pain. It measures the intensity of pain; its interference with vocational, recreational, social, and functional aspects of living; and the extent of associated emotional factors. Patients responded to each item by marking along a 10-cm visual analog scale. Item scores range from 0 to 5, in quarter point increments, and the total score is the sum of the item scores (possible range 0 (no pain)–100 (maximal pain)). A valid NPAD score can be generated if no more than 15% of the items are missing (Scherer et al., 2008). The NPAD has been shown to have validity in comparison to other self-reported pain measures (Goolkasian et al., 2002) as well as supporting constructs of mood and neuroticism (Wheeler et al., 1999). A German version of the NPAD (NPAD-d) was developed recently demonstrating good reliability and validity. Details on the development and on validity and reliability markers of the
NPAD-d have been reported elsewhere (Scherer et al., 2008). Participants of this study completed the NPAD-d. 2.3. Psychological and socio-demographic variables Depressive mood and anxiety were measured by the Hospital Anxiety and Depression Scale (HADS) (Zigmond and Snaith, 1983; Herrmann, 1997; Bjelland et al., 2002), a widely used, short self-assessment questionnaire mainly asking for psychological manifestations of (generalised) anxiety and depressive mood. It consists of two subscales with seven items each. Possible subscale scores range from 0 to 21. According to the German test manual (Herrmann et al., 1995), patients with a depression score >8 were considered depressed and subjects with an anxiety score >10 were considered anxious. Perceived social support was measured by the 14-item short form of the Social Support Questionnaire (‘‘Fragebogen zur Sozialen Unterstützung”; FSozU) (Frydrich et al., 2002). The items refer to different aspects of perceived social support (emotional and instrumental support and social integration), resulting in a global scale with higher scores indicating better social support (five-point scale: from ‘‘relevant‘‘ = 5 to ‘‘not relevant” = 1). The overall score is calculated as the mean score of all completed items. Deficits in social support were defined as having 4 or less points out of a maximum of 5 on the FSozU scale. Age, gender, living with a partner, and education were assessed by single items. Persons who had completed less than 10 years at school were considered to have basic education. Single item questions were used to ask for surgical interventions and injuries of the cervical spine prior to completing the questionnaire, for the number of days with neck pain in the previous year, and for the number of visits with a general practitioner, an orthopaedist, or an anaesthetist. 2.4. Statistical analyses First, descriptive statistics were done to describe the demographic and clinical characteristics of the study sample. The development of the Neck Pain and Disability Scale short version (sfNPAD) was based on the results of the original publication by Wheeler et al. with 100 patients from a hospital setting in the USA. These authors had identified five factors with the set of factors being reduced to four (‘‘neck problems”, ‘‘intensity”, ‘‘effects on emotion and cognition”, ‘‘interference with life activities”) when only one item (item no. 20) loaded on factor 5 (‘‘effect of pain pills”). We rank ordered the NPAD items according to their itemto-total-score correlation – as published by Wheeler and colleagues – by factor subgroup. Then those two items which ranked highest in the ‘‘neck problems”, ‘‘intensity”, ‘‘effects on emotion and cognition”, and ‘‘interference with life activities” subgroup and the single item of the ‘‘effect of pain pills” factor were selected. This resulted in a set of 9 items for the sf-NPAD. For validation of the newly generated sf-NPAD, the dataset of neck pain patients from the German general practice setting was used (described above). Principal component factor analysis was used to investigate the factor structure of the scale. A factor was retained if the Eigenvalue was greater than 1.0. Items were attributed to a factor if factor loadings were >0.5. The sf-NPAD was generated using the same method as for the NPAD original version by summing up the individual item responses (ranging from 0 to 5). No missing items rule was applied for the sf-NPAD as the analyses were done based on the formerly generated complete NPAD item sample. For better comparability with values derived from the NPAD original version, the sf-NPAD score was multiplied by 20/9 to adjust to a 0–100 scale. Internal consistency of the sf-NPAD was evaluated using Cronbach’s alpha and item-to-total-score correlations. The acceptable range of coefficient alpha values is 0.70– 0.90 because assessment instruments with values higher than 0.90
864.e3
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
may suffer from excessive redundancy and those with values less than 0.70 may be unreliable (Nunnally and Bernstein, 1994; Streiner and Norman, 1995; DeVellis, 2003). Construct validity of the sf-NPAD was explored using simple correlations of the sf-NPAD with constructs known to be associated with neck pain (HADS depression subscale, HADS anxiety subscale, FSozU social support scale, number of visits with GPs, orthopaedists, and anaesthetists respectively) and with a neck pain related characteristic not included in the sf-NAPD (number of days with neck pain in previous year) using Pearson’s r coefficients (convergent validity) (Kongsted et al., 2008). Correlation coefficients between 0.1 and 0.3 were considered small, between 0.3 and 0.5 medium, and between 0.5 and 1.0 large. (Cohen, 1988). The discriminative abilities of the sf-NPAD were examined by comparing differences between subgroups stratified on psychological characteristics known to be associated with neck pain. Therefore, t-tests were used to analyse the difference between sf-NPAD mean scores of depressed versus non-depressed persons, of anxious versus non-anxious persons, and of those with deficits in social support versus those without such deficits. All analyses were performed using Stata 9.2 (Stata Corporation, College Station, Texas/USA). There are several reasons why we chose the procedure described above. First, doing the development and validation in the same sample (as opposed to using results from the original hospital setting as published by Wheeler et al.) would have probably led to overfitting of the shortened scale to the present specific German population. Selecting items based on results generated in a different setting allowed us to cross-validate the sf-NPAD in our general practice setting. Another reason to select this approach was that Wheeler et al. selected the NPAD items based on their clinical relevance with respect to ‘‘intensity of pain, its interference with vocational, recreational, social, and functional aspects of living, and the presence and extent of associated emotional factors”
N (%)
Neck pain Number of days with neck pain in previous year Sociodemographic characteristics Age (years) Female Living with a partner Basic education (<10 years at school) Medical history Had cervical spine surgery in the past Had traumaa of the cervical spine in the past Health care utilisation in previous year Number of visits with general practitioner Number of visits with orthopaedist Number of visits with anaesthetist Psychosocial characteristics Depression (HADS depression subscale) (0– 21)b Anxiety (HADS anxiety subscale) (0–21)b Social support (FSozU) (1–5)c
3. Results 3.1. Characteristics of the study sample The mean age of the 448 study participants was 49 ± 16 years. Almost 80% of the study participants were female. One third had basic education, and about one third were unemployed or retired. The mean value of the HADS depression subscale (range 0–21) was 5.4 ± 3.8. Very few participants (7, 1.6%) had had a surgical intervention on the cervical spine, whereas about 20% reported to have had a trauma of the neck. Mean HADS anxiety subscale (range 0– 21) was 8.0 ± 4.1. Perceived social support in the study population was generally high with a mean social support score (range 1–5) of 4.2 ± 0.7 (Table 1). 3.2. Development of the sf-NPAD Based on the results from Wheeler et al., we rank ordered the NPAD items based on their item-to-total-score correlation by the
Table 2 Item-to-total-score correlations of the Neck Pain and Disability Scale (NPAD) original version and short version, ordered by factor subscales according to Wheeler et al. (1999). Item number and factor subgroup NPADa
Table 1 Characteristics of the study sample (N = 448). Characteristics
(Wheeler et al., 1999). The shortened instrument was aimed at measuring these clinical relevant dimensions but in a less redundant way. Furthermore, a set of <10 items would make sure the questionnaire fits on one page. According to our experiences, this would decrease respondent burden and increase the acceptability and applicability of the questionnaire, e.g. in the context of selfadministered multi-domain questionnaires.
Mean (SD; range) 126.6 (114.9; 2–365) 49.4 (15.5, 19–86)
350 (78.1) 340 (76.1) 152 (33.9) 7 (1.6) 81 (19.3)
3.6 (3.6; 0–30) 2.3 (2.3; 1–14) 3.7 (3.3; 0–15) 5.4 (3.8; 0–20) 8.0 (4.1; 0–21) 4.2 (0.7; 1.4–5))
For definition of variables see Section 2. a Trauma due to an accident, an injury, or violence. b HADS denotes Hospital Anxiety and Depression Scale. c FSozU denotes Fragebogen zur Sozialen Unterstützung (Social Support Questionnaire).
Item-to-total-score correlation NPAD total scorea USA sample
Item-to-total-score correlation NPAD short versionb German sample
Factor ‘‘Neck problems” 7 0.667 16 0.675 17 0.762 18 0.583
– 0.712 0.746 –
Factor ‘‘Intensity” 1 2 3 5 6 20
– – 0.633 – 0.726 –
0.593 0.530 0.649 0.626 0.663 0.447
Factor ‘‘Effects on emotion and cognition” 13 0.737 14 0.683 15 0.627
0.743 0.731 –
Factor ‘‘Interference with life activities” 4 0.568 8 0.759 9 0.697 10 0.726 11 0.735 12 0.670 19 0.684
– 0.815 – – 0.757 – –
Factor ‘‘Effect of pain pills” 20 0.447
0.628
In bold: Items with highest ranks in factor subscale, selected for af-NPAD. a Item-to-total-score correlations and item attribution to the five factors is derived from the original publication. Data is taken from Wheeler et al. (1999). b Item-to-total-score correlations of the short version are derived from German general practice setting (Scherer et al., 2008). Original data.
864.e4
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
five factor subgroups. Items No. 16 & 17, 3 & 6, 13 & 14, and 8 & 11 ranked highest in the ‘‘neck problems”, ‘‘intensity”, ‘‘effects on emotion and cognition”, and ‘‘interference with life activities” subgroup. Additionally, item Nr. 20 (‘‘effect of pain pills”) was included. Finally, a set of 9 items were selected for the sf-NPAD (Table 2, left column).
Table 5 Discrimination of the Neck Pain and Disability Scale short form (sf-NPAD) across different psychosocial characteristics. Depressiona Yes
3.3. Psychometric evaluation of the sf-NPAD Cronbach’s alpha of sf-NPAD was 0.88 denoting excellent internal consistency of the scale without being excessively redundant. Item-to-total correlation of the individual sf-NPAD items with the total scale ranged from 0.628 to 0.815 showing consistently significant correlations of the single items with the total scale (Table 2, right column). Exploratory principal component analysis indicated that the sf-NPAD items homogeneously load on a single factor (Table 3). The Eigenvalue of the extracted factor was 4.71, the second factor in the principal component analysis following with an Eigenvalue of 0.89. The extracted factor accounted for 52% of the variance. 3.4. Construct validity Correlation analysis showed significant correlations with criterion variables. Specifically, measures of depression (HADS depression subscale: Pearson’s r = 0.446, p < 0.001) and anxiety (HADS anxiety subscale: Pearson’s r = 0.399, p < 0.001) were appreciably correlated with sf-NPAD values showing correlations of medium magnitude. The number of days with neck pain in the previous year, a neck pain related characteristic not included in the sf-NPAD, showed also a significant medium magnitude correlation with the
No
D (95%CI)
pd
N = 86
N = 359
sf-NPAD-d
60.5 ± 18.3
45.2 ± 18.3
15.4 (11.1, 16.6)
<0.001
sf-NPAD-d
Anxietyb N = 123 56.8 ± 19.1
N = 322 44.8 ± 18.1
12.0 (8.2, 15.8)
<0.001
sf-NPAD-d
Deficits in social supportc N = 152 N = 296 52.1 ± 19.1 45.9 ± 18.9
6.2(2.5, 9.9)
0.0011
d
p-Values derived from t-tests for mean scores. a According to the depression subscale of the Hospital Anxiety and Depression Scale. b According to the anxiety subscale of the Hospital Anxiety and Depression Scale. c According to ‘‘Fragebogen zur Sozialen Unterstützung” (Social Support Questionnaire).
shortened instrument (Pearson’s r = 0.326, p < 0.001). Additionally, number of visits with an anaesthetist (Pearson’s r = 0.651, p = 0.0064) was even highly correlated with the sf-NPAD. Other measures of health care use (number of visits with a GP: Pearson’s r = 0.221, p < 0.001; number of visits with an orthopaedist: Pearson’s r = 0.226, p = 0.018) were also significantly correlated but showed only small correlations. A small but statistically significant correlation was also identified for social support (FSozU: Pearson’s r = 0.195, p < 0.001), see Table 4. 3.5. Discriminative validity
Table 3 Factor structure of the Neck Pain and Disability Scale short form (sf-NPAD).
a b
Item nmber NPADa
Factor loadingb
3 6 8 11 13 14 16 17 20
0.621 0.728 0.823 0.764 0.747 0.733 0.711 0.749 0.612
4. Discussion and conclusions
NPAD denotes Neck Pain and Disability Scale. Single factor, derived from principal component factor analysis.
Table 4 Correlation analysis of the Neck Pain and Disability Scale short form (sf-NPAD) with psychosocial, clinical and health care utilisation characteristics. Characteristics HADSa depression subscale HADSa anxiety subscale FSozUb social support scale Number of days with neck pain in previous year Number of visits with general practitioner in previous year Number of visits with orthopaedist in previous year Number of visits with anaesthetist in previous year
An analysis of the sf-NAPD and its ability to discriminate between subgroups of patients with different neck pain-related characteristics are shown in Table 5. Based on depression symptoms, anxiety symptoms, as well as deficits in social support the sf-NPAD distinguished between these groups with a high level of significance.
sf-NAPD 0.446 0.399 0.195 0.326 0.221 0.226 0.651
Denotes 0.01 6 p < 0.05; denotes 0.001 6 p < 0.01; denotes p < 0.001. pValues derived from Pearson’s correlation analysis. a HADS denotes Hospital Anxiety and Depression Scale. b FSozU denotes Fragebogen zur Sozialen Unterstützung (Social Support Questionnaire).
This study proposes a 9-item shortened version of the Neck Pain and Disability Scale based on the selection of clinically relevant dimensions of neck pain and related disability. It includes aspects of neck pain intensity, problems with neck movement, neck pain effects on emotion and cognition, its interference with life activities, and the effect of pain pills. The newly developed sf-NPAD showed construct and discriminative validity when compared with clinical, psychosocial, and health care utilisation markers and it demonstrated substantial internal consistency. To increase generalisability, results from two different samples were used for development and validation of the short version. The scale development was based on patients from a hospital setting in the USA. Validity and reliability were evaluated in a general practice setting in Germany, an independent sample from a culturally and clinically different context. Several limitations should be considered. First, the scale has only been tested in a single setting. Due to the eligibility criteria of the study, persons who consulted their GP because of a new trauma due to an accident, an injury, or violence, who were terminally ill, suffered from cancer, were in need of nursing care or had severe cognitive impairment were excluded from this sample. The applicability of the scale in other clinical and research settings, and
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
generalisability to other populations of neck pain patients has to be evaluated further. Secondly, the evaluation sample demonstrates a rather large number of exclusions. However, the study was conducted in a relatively large group recruited by a defined algorithm from the whole patient population of various practices (Fig. 1), and the exclusions can be traced back to predefined reasons according to this algorithm. Thirdly, the evaluation of the newly developed scale has been done using the German translation of the NPAD, the NPAD-d (Scherer et al., 2008). Finally, the instrument has not been tested for aspects of reliability beyond internal consistency and for sensitivity to change, to detect change over time, or for feasibility and clinical utility. Further studies are needed to evaluate these properties of the measure, and to evaluate it in separate settings and language versions. This study does, however, provide a useful first step for a shortened neck pain assessment instrument. Another potential limitation is related to the factor structure of the original NPAD instrument which was used as a basis for development of the shortened instrument. Previous studies evaluating other language versions of the NPAD original version could not replicate the 4–5 factor structures as proposed by Wheeler et al. In contrast, these evaluations revealed major instability in the factor structure of the scale with frequent cross-loading or non-loading of items and with 1–3 factors extracted (Goolkasian et al., 2002; Wlodyka-Demaille et al., 2002; Cook et al., 2006; Scherer et al., 2008; Bremerich et al., 2008; Monticone et al., 2008). However, as opposed to the meaning of these statistics in research settings, psychometric analyses may not reflect all aspects that are relevant for clinical practice (Delis et al., 2003). For selection of an approach to shorten the scale we focused on clin-
864.e5
ical relevance and downgraded psychometric instabilities. The factor structure proposed by Wheeler et al. has face validity and reflects clinically relevant dimensions of neck pain and related disability. Generally, a short version can be generated in different ways (Blozik et al., 2007; Barber et al., 2005; Melzack, 1987; Bohus et al., 2009). However, if one would have focused on the absolute item-to-total scale rank order, the highly clinically relevant question about the effect of pain pills would have been missed. As for this item, we suggest to add ‘‘If you ever took pain pills for neck pain. . .”. This question revealed to have a notably higher number of missing values (Scherer et al., 2008), probably due to persons not taking pain pills who were confused. As for a missing items rule for the sf-NPAD we propose to apply the same that is used for the 20-item version (Scherer et al., 2008) which, in particular, means that no more than 15% of the sf-NPAD items should be missing. In conclusion, the 9-item sf-NPAD seems to be a valid and internally consistent abbreviation of the 20-item NPAD original version. Thus the sf-NPAD may be a useful tool in the assessment and management process of neck pain and in neck pain-related research.
Acknowledgement The study was supported by the German Ministry of Education and Research (BMBF), Grant No. 01 GK 0516. MS was funded by a Young Investigators Award of the BMBF. We are grateful to the practitioners and participants involved in this study.
1308 consulted general practitioner because of neck pain in previous 12 months
excluded: 80 did fulfil inclusion criteria 1228 invited to participate
excluded: 745 were not willing to participate
483 received questionnaire
excluded: 22 did not complete or return questionnaire 461 completed questionnaire
13 no NPAD-d score available: > 3 NPAD-d items missing 448 analytic study sample: valid NPAD-d score available Fig. 1. Flowchart of participants of the evaluation sample.
864.e6
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
References Agarwal S, Allison GT, Agarwal A, Singer KP. Reliability and validity of the Hindi version of the Neck Pain and Disability Scale in cervical radiculopathy patients. Disabil Rehabil 2006;28:1405–11. Barber MD, Walters MD, Bump RC. Short forms of two condition-specific quality-oflife questionnaires for women with pelvic floor disorders (PFDI-20 and PFIQ-7). Am J Obstet Gynecol 2005;193(1):103–13. Bicer A, Yazici A, Camdeviren H, Erdogan C. Assessment of pain and disability in patients with chronic neck pain: reliability and construct validity of the Turkish version of the Neck Pain and Disability Scale. Disabil Rehabil 2004;26:959–62. Bjelland I, Dahl AA, Haug TT, Neckelmann D. The validity of the Hospital Anxiety and Depression Scale. An updated literature review. J Psychosom Res 2002;52(2):69–77. Blozik E, Stuck AE, Niemann S, Ferrell BA, Harari D, von Renteln-Kruse W, et al. Geriatric Pain Measure short form: development and initial evaluation. J Am Geriatr Soc 2007;55:2045–50. Bohus M, Kleindienst N, Limberger MF, Stieglitz RD, Domsalla M, Chapman AL, et al. The short version of the Borderline Symptom List (BSL-23): development and initial data on psychometric properties. Psychopathology 2009;42(1):32–9. Bolton JE. Sensitivity and specificity of outcome measures in patients with neck pain: detecting clinically significant improvement. Spine 2004;29:2410–7. Bremerich FH, Grob D, Dvorak J, Mannion AF. The Neck Pain and Disability Scale: cross-cultural adaptation into German and evaluation of its psychometric properties in chronic neck pain and C1-2 fusion patients. Spine 2008;33(9):1018–27. Carroll LJ, Hogg-Johnson S, van der Velde G, Haldeman S, Holm LW, Carragee EJ, et al. Bone and Joint Decade 2000–2010 Task Force on Neck Pain and Its Associated Disorders. Course and prognostic factors for neck pain in the general population: results of the Bone and Joint Decade 2000–2010 Task Force on Neck Pain and Its Associated Disorders. Spine 2008;33(4 Suppl):S75–82. Cohen J. Statistical power analysis for the behavioral sciences. 2nd ed. New York (NY): Academic Press; 1988. Cook C, Richardson JK, Braga L, Menezes A, Soler X, Kume P, et al. Cross-cultural adaptation and validation of the Brazilian Portuguese version of the neck disability index and Neck Pain and Disability Scale. Spine 2006;31:1621–7. Cote P, Cassidy D, Carroll L. The Saskatchewan health and back pain survey: the prevalence of neck pain and related disability in Saskatchewan adults. Spine 1998;23:1689–98. Delis DC, Jacobson M, Bondi MW, Hamilton JM, Salmon DP. The myth of testing construct validity using factor analysis or correlations with normal or mixed clinical populations: lessons from memory assessment. J Int Neuropsychol Soc 2003;9:936–46. DeVellis RF. Scale development: theory and applications. 2nd ed. Newbury Park (CA): Sage; 2003. Deyo RA, Andersson G, Bombardier C, Cherkin DC, Keller RB, Lee CK, et al. Outcome measures for studying patients with low back pain. Spine 1994;19:2032S–6S. Eaker S, Bergström R, Bergström A, Adami HO, Nyren O. Response rate to mailed epidemiologic questionnaires: a population-based randomized trial of variations in design and mailing routines. Am J Epidemiol 1998;147:74–82. Frydrich T, Sommer G, Brähler E. F-SozU – Fragebogen zur Sozialen Unterstützung. In: Brähler E, Schumacher J, Strauß B, editors. Diagnostische Verfahren in der Psychotherapie. Göttingen: Hogrefe; 2002. Goolkasian P, Wheeler AH, Gretz SS. The Neck Pain and Disability Scale: test–retest reliability and construct validity. Clin J Pain 2002;18:245–50. Herrmann C. International experiences with the Hospital Anxiety and Depression Scale – a review of validation data and clinical results. J Psychosom Res 1997;42(1):17–41.
Herrmann CH, Buss U, Snaith RP. HADS-D – Hospital Anxiety and Depression ScaleDeutsche Version: Ein Fragebogen zur Erfassung von Angst und Depressivität in der somatischen Medizin. Bern: Hans Huber; 1995. Jordan A, Manniche C, Mosdal C, Hindsberger C. The Copenhagen Neck Functional Disability Scale: a study of reliability and validity. J Manipul Physiol Ther 1998;21:520–7. Kongsted A, Bendix T, Qerama E, Kasch H, Bach FW, Korsholm L, et al. Acute stress response and recovery after whiplash injuries. A one-year prospective study. Eur J Pain 2008;12:455–63. Kose G, Hepguler S, Atamaz F, Oder G. A comparison of four disability scales for Turkish patients with neck pain. J Rehabil Med. 2007;39:358–62. Leak AM, Cooper J, Dyer S, Williams KA, Turner-Stokes L, Frank AO. The Northwick park Neck Pain Questionnaire, devised to measure neck pain and disability. Br J Rheumatol 1994;33:469–74. Lee H, Nicholson LL, Adams RD, Maher CG, Halaki M, Bae SS. Development and psychometric testing of Korean language versions of 4 neck pain and disability questionnaires. Spine 2006;31:1841–5. Melzack R. The short-form McGill Pain Questionnaire. Pain 1987;30(2):191–7. Monticone M, Baiardi P, Nido N, Righini C, Tomba A, Giovanazzi E. Development of the Italian version of the Neck Pain and Disability Scale, NPDS-I: cross-cultural adaptation, reliability, and validity. Spine 2008;33:E429–34. Mousavi SJ, Parnianpour M, Montazeri A, Mehdian H, Karimi A, Abedi M, et al. Translation and validation study of the Iranian versions of the neck disability index and the Neck Pain and Disability Scale. Spine 2007;32: E825–31. Nunnally JC, Bernstein IH. Psychometric theory. 3rd ed. New York (NY): McGraw Hill; 1994. Pietrobon R, Coeytaux RR, Carey S, et al. Standard scales for measurement of functional outcome for cervical pain or dysfunction. A systematic review. Spine 2002;27:515–22. Resnick DN. Subjective outcome assessments for cervical spine pathology: a narrative review. J Chiropr Med 2005;4:113–34. Scherer M, Blozik E, Himmel W, Laptinskaya D, Kochen MM, Herrmann-Lingen C. Psychometric properties of a German version of the Neck Pain and Disability Scale. Eur Spine J 2008;17:922–9. Streiner DJ, Norman GR. Health measurement scales: a practical guide to their development and use. 2nd ed. Oxford: Oxford University Press; 1995. Vernon H, Mior S. The neck disability index: a study of reliability and validity. J Manipul Physiol Ther 1991;14:409–15. Westaway MD, Stratford PW, Binkley JM. The patient-specific functional scale: validation of its use in persons with neck dysfunction. J Orthop Sports Phys Ther 1998;27:331–8. Wetzel D, Himmel W, Heidenreich R, Hummers-Pradier E, Kochen MM, Rogausch A, et al. Participation in a quality of care study and consequences for generalizability of general practice research. Fam Pract 2005;22:458–64. Wheeler AH, Goolkasian P, Baird AC, Darden 2nd BV. Development of the Neck Pain and Disability Scale. Item analysis, face, and criterion-related validity. Spine 1999;24:1290–4. Wlodyka-Demaille S, Poiraudeau S, Catanzariti JF, Rannou F, Fermanian J, Revel M. French translation and validation of 3 functional disability scales for neck pain. Arch Phys Med Rehabil 2002;83:376–82. Wlodyka-Demaille S, Poiraudeau S, Catanzariti JF, Rannou F, Fermanian J, Revel M. The ability to change of three questionnaires for neck pain. Joint Bone Spine 2004;71:317–26. Wlodyka-Demaille S, Poiraudeau S, Fermanian J, Catanzariti JF, Rannou F, Revel M. French translation and validation of a functional disability scale for neck pain. Ann Readapt Med Phys 2001;44:132–42. Zigmond AS, Snaith RP. The Hospital Anxiety and Depression Scale. Acta Psychiat Scand 1983;67(6):361–70.
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
864.e7
Appendix 1 Items and scoring rules of Neck Pain and Disability Scale original version (NPAD) and Neck Pain and Disability Scale short form (sf-NPAD). 1. How bad is your pain today? No pain
│___0___│___1___│___2___│___3___│___4___│___5___│ Most severe pain
2. How bad is your pain on the average? No pain
│___0___│___1___│___2___│___3___│___4___│___5___│ Most severe pain
3. How bad is your pain at its worst? No pain
│___0___│___1___│___2___│___3___│___4___│___5___│ Cannot tolerate
4. Does your pain interfere with your sleep? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Can’t sleep
5. How bad is your pain with standing? No pain
│___0___│___1___│___2___│___3___│___4___│___5___│ Most severe pain
6. How bad is your pain with walking? No pain
│___0___│___1___│___2___│___3___│___4___│___5___│ Most severe pain
7. Does your pain interfere with driving or riding a car? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Can’t drive or ride
8. Does your pain interfere with social activities? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Always
9. Does your pain interfere with recreational activities? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Always
10. Does your pain interfere with work activities? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Can’t work
11. Does your pain interfere with your personal care (eating, bathing, dressing, etc)? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Always
12. Does your pain interfere with your personal relationships (family, friends, sex, etc)? Not at all
│___0___│___1___│___2___│___3___│___4___│___5___│ Always
13. How has your pain changed your outlook on life and the future (depression, hopelessness)? No change│___0___│___1___│___2___│___3___│___4___│___5___│ Complete change
14. Does pain affect your emotions? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Completely
15. Does your pain affect your ability to think or concentrate? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Completely
16. How stiff is your neck? Not stiff
│___0___│___1___│___2___│___3___│___4___│___5___│ Can’t move neck
17. How much trouble do you have turning your neck? No trouble│___0___│___1___│___2___│___3___│___4___│___5___│ Can’t move neck
18. How much trouble do you have looking up or down? No trouble │___0___│___1___│___2___│___3___│___4___│___5___│ Can’t look up or down
19. How much trouble do you have working overhead? No trouble │___0___│___1___│___2___│___3___│___4___│___5___│Can´t work overhead
20. How much do pain pills help? Complete relief │___0___│___1___│___2___│___3___│___4___│___5___│ No relief
Items included in sf-NPAD are marked in light grey. Calculation of NPAD original score: total score (0–100) = sum of all items (0–5). Calculation of sf-NPAD score: total score (0–45) = sum of all items (0–5); transformation to a 0–100 scale by multiplying the raw total score by 20/9.
Contents lists available at ScienceDirect
European Journal of Pain journal homepage: www.EuropeanJournalPain.com
Development of a short version of the Neck Pain and Disability Scale Eva Blozik a,b,*, Michael M. Kochen a, Christoph Herrmann-Lingen c, Martin Scherer a,b a
Department of General Practice and Family Medicine, University of Göttingen, Humboldtallee 38, 37073 Göttingen, Germany Institute of Social Medicine, Universitätsklinikum Schleswig-Holstein, Beckergrube 43-47, 23552 Lübeck, Germany c Department of Psychosomatic Medicine and Psychotherapy, University of Göttingen, von-Siebold-Str. 5, 37075 Göttingen, Germany b
a r t i c l e
i n f o
Article history: Received 8 July 2009 Received in revised form 1 December 2009 Accepted 13 December 2009 Available online 21 January 2010 Keywords: Neck pain Pain measurement Psychometrics Questionnaire Pain assessment
a b s t r a c t Previous evaluations of the 20-item Neck Pain and Disability Scale (NPAD) were indicative of excessive redundancy of the measure. The aim of this study was to develop a shortened version of the NPAD (sf-NPAD) based on results of item-to-total-score correlations and factor analysis as published by the developers of the original NPAD. Two items with the highest item-to-total score correlation were selected per factor subscale with the exception of one factor consisting of only one item. This resulted in the selection of 9 items for the sf-NPAD. The sf-NPAD was validated in a separate sample of 448 neck pain patients from 15 general practices in the area of Göttingen/Germany. Participants completed the 20-item NPAD German version and gave additional sociodemographic and clinical information. Psychometric properties of the sf-NPAD were evaluated using Cronbach’s alpha, item-to-total-score correlation, and unrestricted principal factor analysis. Construct validity was evaluated by Pearson’s r with clinical characteristics. Discriminative validity was examined by comparing differences between subgroups stratified by psychosocial characteristics using t-tests for mean scores. Cronbach’s alpha of the sf-NPAD was 0.88. Item-to-total-scale correlations ranged between 0.628 and 0.815, and sf-NPAD items homogeneously loaded on a single factor. Correlation analysis showed high correlations with criterion variables. The sf-NPAD scores of patient subgroups were significantly different showing good discriminative validity. In conclusion, the sf-NPAD demonstrated good validity and internal consistency in this general practice setting. The abbreviated version may facilitate applicability of the scale in clinical and research settings. Ó 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.
1. Introduction The assessment of pain of the spine is important in evaluating treatment effects and patient outcomes (Deyo et al., 1994). Neck pain is a highly prevalent condition with about two thirds of the adult population affected at some time in their lives (Cote et al., 1998). There are 11 measurement scales validated for the use in neck pain patients (Resnick 2005).The most commonly used selfreport instruments are the Neck Disability Index (Vernon and Mior, 1991), the Copenhagen Neck Functional Disability Scale (Jordan et al. 1998), the Northwick Park Neck Pain Questionnaire (Leak et al., 1994), the Neck Pain and Disability Scale (Wheeler et al., 1999), and the Patient-Specific Functional Scale (Westaway et al., 1998). These scales are generally considered to be comparable in terms of their validity and reliability (Pietrobon et al., 2002;
* Corresponding author. Address: Department of General Practice and Family Medicine, University of Göttingen, Humboldtallee 38, 37073 Göttingen, Germany. Tel.: +49 451 799 2530; fax: +49 451 799 2522. E-mail address: [email protected] (E. Blozik).
Resnick, 2005). The choice of the appropriate instrument should therefore depend on the particular patient population, the specific application context, and the ease of use for the patient and ease of scoring for the clinician (Pietrobon et al., 2002; Resnick, 2005). Prior to the development of the Neck Pain and Disability Scale (NPAD), none of the existing instruments designed for the measurement of neck pain problems adequately assessed the multidimensional effects of neck pain (Resnick, 2005). The NPAD measures problems with neck movements, pain intensity, effects on emotion and cognition, and the level of interference with daily life activities. The NPAD has shown to be responsive to treatment (Bolton, 2004; Goolkasian et al., 2002), to correlate with the patient’s global assessment of outcome (Wlodyka-Demaille et al., 2004), and to have robust construct validity (Wlodyka-Demaille et al., 2002). It has been found easy to complete for patients and is simple to score (Wheeler et al., 1999). Originally developed in the USA, the NPAD was translated to various languages (e.g. Wlodyka-Demaille et al., 2001; Bicer et al., 2004; Cook et al., 2006; Agarwal et al., 2006; Mousavi et al., 2007) including a recently introduced German version (Scherer et al., 2008).
1090-3801/$36.00 Ó 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ejpain.2009.12.006
864.e2
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
However, results of previous research indicated that the NPAD may suffer from excessive redundancy. Cronbach‘s alpha values reported in these earlier studies were 0.93 (Wheeler et al., 1999; Goolkasian et al., 2002) and 0.94 (Lee et al., 2006; Kose et al., 2007; Monticone et al., 2008; Scherer et al., 2008), with values higher than 0.90 being indicative of excessive redundancy of the scale (Nunnally and Bernstein, 1994; Streiner and Norman, 1995; DeVellis, 2003). Furthermore, individual characteristics predicting course and prognosis of neck pain should be assessed in patients in addition to the neck problem itself leading to a considerable length of the overall questionnaire (Carroll et al., 2008). However, lengthy questionnaires are generally more vulnerable to missing values and refusal (Eaker et al., 1998). An abbreviated version of the NPAD would be easier to use for neck pain assessment in clinical processes and in neck pain-related research. It would likely increase its acceptability and applicability, e.g. in multidimensional questionnaires, and reduce respondent burden. The aim of this research was to develop a shortened version of the NPAD. 2. Methods 2.1. Study design This is a survey of patients from a primary care setting in Germany with at least one onset of neck pain between March 2005 and April 2006. The study was approved by the local research ethics committee. As part of a project on the quality of medical care in general practice (MedViP), a network of 104 general practices has been established (Wetzel et al., 2005). A convenience sample of 15 of these practices within a radius of 30 km around Göttingen, a medium-sized town in Germany, were selected for participation and provided anonymised electronic patient data (year of birth, sex, diagnosis). Patients were included in a list of potentially eligible persons if at least one consultation because of neck pain was documented in the electronic patient record during the study period. All general practitioners were asked to exclude patients from this list, if they had a neck pain consultation because of a new trauma due to an accident, an injury, or violence, were terminally ill, suffered from cancer, were in need of nursing care or had severe cognitive impairment. Additionally, patients seen by locums only, patients who had moved to a region outside of the study area or who were not able to speak German were excluded from the study. Participants received a comprehensive self-administered questionnaire covering socio-demographic information, anxiety, depression, social support, and neck pain. 2.2. Neck and Pain Disability Scale (NPAD) (Wheeler et al., 1999; Goolkasian et al., 2002) The NPAD is a 20-item measure that was specifically developed for patients with neck pain. It measures the intensity of pain; its interference with vocational, recreational, social, and functional aspects of living; and the extent of associated emotional factors. Patients responded to each item by marking along a 10-cm visual analog scale. Item scores range from 0 to 5, in quarter point increments, and the total score is the sum of the item scores (possible range 0 (no pain)–100 (maximal pain)). A valid NPAD score can be generated if no more than 15% of the items are missing (Scherer et al., 2008). The NPAD has been shown to have validity in comparison to other self-reported pain measures (Goolkasian et al., 2002) as well as supporting constructs of mood and neuroticism (Wheeler et al., 1999). A German version of the NPAD (NPAD-d) was developed recently demonstrating good reliability and validity. Details on the development and on validity and reliability markers of the
NPAD-d have been reported elsewhere (Scherer et al., 2008). Participants of this study completed the NPAD-d. 2.3. Psychological and socio-demographic variables Depressive mood and anxiety were measured by the Hospital Anxiety and Depression Scale (HADS) (Zigmond and Snaith, 1983; Herrmann, 1997; Bjelland et al., 2002), a widely used, short self-assessment questionnaire mainly asking for psychological manifestations of (generalised) anxiety and depressive mood. It consists of two subscales with seven items each. Possible subscale scores range from 0 to 21. According to the German test manual (Herrmann et al., 1995), patients with a depression score >8 were considered depressed and subjects with an anxiety score >10 were considered anxious. Perceived social support was measured by the 14-item short form of the Social Support Questionnaire (‘‘Fragebogen zur Sozialen Unterstützung”; FSozU) (Frydrich et al., 2002). The items refer to different aspects of perceived social support (emotional and instrumental support and social integration), resulting in a global scale with higher scores indicating better social support (five-point scale: from ‘‘relevant‘‘ = 5 to ‘‘not relevant” = 1). The overall score is calculated as the mean score of all completed items. Deficits in social support were defined as having 4 or less points out of a maximum of 5 on the FSozU scale. Age, gender, living with a partner, and education were assessed by single items. Persons who had completed less than 10 years at school were considered to have basic education. Single item questions were used to ask for surgical interventions and injuries of the cervical spine prior to completing the questionnaire, for the number of days with neck pain in the previous year, and for the number of visits with a general practitioner, an orthopaedist, or an anaesthetist. 2.4. Statistical analyses First, descriptive statistics were done to describe the demographic and clinical characteristics of the study sample. The development of the Neck Pain and Disability Scale short version (sfNPAD) was based on the results of the original publication by Wheeler et al. with 100 patients from a hospital setting in the USA. These authors had identified five factors with the set of factors being reduced to four (‘‘neck problems”, ‘‘intensity”, ‘‘effects on emotion and cognition”, ‘‘interference with life activities”) when only one item (item no. 20) loaded on factor 5 (‘‘effect of pain pills”). We rank ordered the NPAD items according to their itemto-total-score correlation – as published by Wheeler and colleagues – by factor subgroup. Then those two items which ranked highest in the ‘‘neck problems”, ‘‘intensity”, ‘‘effects on emotion and cognition”, and ‘‘interference with life activities” subgroup and the single item of the ‘‘effect of pain pills” factor were selected. This resulted in a set of 9 items for the sf-NPAD. For validation of the newly generated sf-NPAD, the dataset of neck pain patients from the German general practice setting was used (described above). Principal component factor analysis was used to investigate the factor structure of the scale. A factor was retained if the Eigenvalue was greater than 1.0. Items were attributed to a factor if factor loadings were >0.5. The sf-NPAD was generated using the same method as for the NPAD original version by summing up the individual item responses (ranging from 0 to 5). No missing items rule was applied for the sf-NPAD as the analyses were done based on the formerly generated complete NPAD item sample. For better comparability with values derived from the NPAD original version, the sf-NPAD score was multiplied by 20/9 to adjust to a 0–100 scale. Internal consistency of the sf-NPAD was evaluated using Cronbach’s alpha and item-to-total-score correlations. The acceptable range of coefficient alpha values is 0.70– 0.90 because assessment instruments with values higher than 0.90
864.e3
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
may suffer from excessive redundancy and those with values less than 0.70 may be unreliable (Nunnally and Bernstein, 1994; Streiner and Norman, 1995; DeVellis, 2003). Construct validity of the sf-NPAD was explored using simple correlations of the sf-NPAD with constructs known to be associated with neck pain (HADS depression subscale, HADS anxiety subscale, FSozU social support scale, number of visits with GPs, orthopaedists, and anaesthetists respectively) and with a neck pain related characteristic not included in the sf-NAPD (number of days with neck pain in previous year) using Pearson’s r coefficients (convergent validity) (Kongsted et al., 2008). Correlation coefficients between 0.1 and 0.3 were considered small, between 0.3 and 0.5 medium, and between 0.5 and 1.0 large. (Cohen, 1988). The discriminative abilities of the sf-NPAD were examined by comparing differences between subgroups stratified on psychological characteristics known to be associated with neck pain. Therefore, t-tests were used to analyse the difference between sf-NPAD mean scores of depressed versus non-depressed persons, of anxious versus non-anxious persons, and of those with deficits in social support versus those without such deficits. All analyses were performed using Stata 9.2 (Stata Corporation, College Station, Texas/USA). There are several reasons why we chose the procedure described above. First, doing the development and validation in the same sample (as opposed to using results from the original hospital setting as published by Wheeler et al.) would have probably led to overfitting of the shortened scale to the present specific German population. Selecting items based on results generated in a different setting allowed us to cross-validate the sf-NPAD in our general practice setting. Another reason to select this approach was that Wheeler et al. selected the NPAD items based on their clinical relevance with respect to ‘‘intensity of pain, its interference with vocational, recreational, social, and functional aspects of living, and the presence and extent of associated emotional factors”
N (%)
Neck pain Number of days with neck pain in previous year Sociodemographic characteristics Age (years) Female Living with a partner Basic education (<10 years at school) Medical history Had cervical spine surgery in the past Had traumaa of the cervical spine in the past Health care utilisation in previous year Number of visits with general practitioner Number of visits with orthopaedist Number of visits with anaesthetist Psychosocial characteristics Depression (HADS depression subscale) (0– 21)b Anxiety (HADS anxiety subscale) (0–21)b Social support (FSozU) (1–5)c
3. Results 3.1. Characteristics of the study sample The mean age of the 448 study participants was 49 ± 16 years. Almost 80% of the study participants were female. One third had basic education, and about one third were unemployed or retired. The mean value of the HADS depression subscale (range 0–21) was 5.4 ± 3.8. Very few participants (7, 1.6%) had had a surgical intervention on the cervical spine, whereas about 20% reported to have had a trauma of the neck. Mean HADS anxiety subscale (range 0– 21) was 8.0 ± 4.1. Perceived social support in the study population was generally high with a mean social support score (range 1–5) of 4.2 ± 0.7 (Table 1). 3.2. Development of the sf-NPAD Based on the results from Wheeler et al., we rank ordered the NPAD items based on their item-to-total-score correlation by the
Table 2 Item-to-total-score correlations of the Neck Pain and Disability Scale (NPAD) original version and short version, ordered by factor subscales according to Wheeler et al. (1999). Item number and factor subgroup NPADa
Table 1 Characteristics of the study sample (N = 448). Characteristics
(Wheeler et al., 1999). The shortened instrument was aimed at measuring these clinical relevant dimensions but in a less redundant way. Furthermore, a set of <10 items would make sure the questionnaire fits on one page. According to our experiences, this would decrease respondent burden and increase the acceptability and applicability of the questionnaire, e.g. in the context of selfadministered multi-domain questionnaires.
Mean (SD; range) 126.6 (114.9; 2–365) 49.4 (15.5, 19–86)
350 (78.1) 340 (76.1) 152 (33.9) 7 (1.6) 81 (19.3)
3.6 (3.6; 0–30) 2.3 (2.3; 1–14) 3.7 (3.3; 0–15) 5.4 (3.8; 0–20) 8.0 (4.1; 0–21) 4.2 (0.7; 1.4–5))
For definition of variables see Section 2. a Trauma due to an accident, an injury, or violence. b HADS denotes Hospital Anxiety and Depression Scale. c FSozU denotes Fragebogen zur Sozialen Unterstützung (Social Support Questionnaire).
Item-to-total-score correlation NPAD total scorea USA sample
Item-to-total-score correlation NPAD short versionb German sample
Factor ‘‘Neck problems” 7 0.667 16 0.675 17 0.762 18 0.583
– 0.712 0.746 –
Factor ‘‘Intensity” 1 2 3 5 6 20
– – 0.633 – 0.726 –
0.593 0.530 0.649 0.626 0.663 0.447
Factor ‘‘Effects on emotion and cognition” 13 0.737 14 0.683 15 0.627
0.743 0.731 –
Factor ‘‘Interference with life activities” 4 0.568 8 0.759 9 0.697 10 0.726 11 0.735 12 0.670 19 0.684
– 0.815 – – 0.757 – –
Factor ‘‘Effect of pain pills” 20 0.447
0.628
In bold: Items with highest ranks in factor subscale, selected for af-NPAD. a Item-to-total-score correlations and item attribution to the five factors is derived from the original publication. Data is taken from Wheeler et al. (1999). b Item-to-total-score correlations of the short version are derived from German general practice setting (Scherer et al., 2008). Original data.
864.e4
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
five factor subgroups. Items No. 16 & 17, 3 & 6, 13 & 14, and 8 & 11 ranked highest in the ‘‘neck problems”, ‘‘intensity”, ‘‘effects on emotion and cognition”, and ‘‘interference with life activities” subgroup. Additionally, item Nr. 20 (‘‘effect of pain pills”) was included. Finally, a set of 9 items were selected for the sf-NPAD (Table 2, left column).
Table 5 Discrimination of the Neck Pain and Disability Scale short form (sf-NPAD) across different psychosocial characteristics. Depressiona Yes
3.3. Psychometric evaluation of the sf-NPAD Cronbach’s alpha of sf-NPAD was 0.88 denoting excellent internal consistency of the scale without being excessively redundant. Item-to-total correlation of the individual sf-NPAD items with the total scale ranged from 0.628 to 0.815 showing consistently significant correlations of the single items with the total scale (Table 2, right column). Exploratory principal component analysis indicated that the sf-NPAD items homogeneously load on a single factor (Table 3). The Eigenvalue of the extracted factor was 4.71, the second factor in the principal component analysis following with an Eigenvalue of 0.89. The extracted factor accounted for 52% of the variance. 3.4. Construct validity Correlation analysis showed significant correlations with criterion variables. Specifically, measures of depression (HADS depression subscale: Pearson’s r = 0.446, p < 0.001) and anxiety (HADS anxiety subscale: Pearson’s r = 0.399, p < 0.001) were appreciably correlated with sf-NPAD values showing correlations of medium magnitude. The number of days with neck pain in the previous year, a neck pain related characteristic not included in the sf-NPAD, showed also a significant medium magnitude correlation with the
No
D (95%CI)
pd
N = 86
N = 359
sf-NPAD-d
60.5 ± 18.3
45.2 ± 18.3
15.4 (11.1, 16.6)
<0.001
sf-NPAD-d
Anxietyb N = 123 56.8 ± 19.1
N = 322 44.8 ± 18.1
12.0 (8.2, 15.8)
<0.001
sf-NPAD-d
Deficits in social supportc N = 152 N = 296 52.1 ± 19.1 45.9 ± 18.9
6.2(2.5, 9.9)
0.0011
d
p-Values derived from t-tests for mean scores. a According to the depression subscale of the Hospital Anxiety and Depression Scale. b According to the anxiety subscale of the Hospital Anxiety and Depression Scale. c According to ‘‘Fragebogen zur Sozialen Unterstützung” (Social Support Questionnaire).
shortened instrument (Pearson’s r = 0.326, p < 0.001). Additionally, number of visits with an anaesthetist (Pearson’s r = 0.651, p = 0.0064) was even highly correlated with the sf-NPAD. Other measures of health care use (number of visits with a GP: Pearson’s r = 0.221, p < 0.001; number of visits with an orthopaedist: Pearson’s r = 0.226, p = 0.018) were also significantly correlated but showed only small correlations. A small but statistically significant correlation was also identified for social support (FSozU: Pearson’s r = 0.195, p < 0.001), see Table 4. 3.5. Discriminative validity
Table 3 Factor structure of the Neck Pain and Disability Scale short form (sf-NPAD).
a b
Item nmber NPADa
Factor loadingb
3 6 8 11 13 14 16 17 20
0.621 0.728 0.823 0.764 0.747 0.733 0.711 0.749 0.612
4. Discussion and conclusions
NPAD denotes Neck Pain and Disability Scale. Single factor, derived from principal component factor analysis.
Table 4 Correlation analysis of the Neck Pain and Disability Scale short form (sf-NPAD) with psychosocial, clinical and health care utilisation characteristics. Characteristics HADSa depression subscale HADSa anxiety subscale FSozUb social support scale Number of days with neck pain in previous year Number of visits with general practitioner in previous year Number of visits with orthopaedist in previous year Number of visits with anaesthetist in previous year
An analysis of the sf-NAPD and its ability to discriminate between subgroups of patients with different neck pain-related characteristics are shown in Table 5. Based on depression symptoms, anxiety symptoms, as well as deficits in social support the sf-NPAD distinguished between these groups with a high level of significance.
sf-NAPD 0.446 0.399 0.195 0.326 0.221 0.226 0.651
Denotes 0.01 6 p < 0.05; denotes 0.001 6 p < 0.01; denotes p < 0.001. pValues derived from Pearson’s correlation analysis. a HADS denotes Hospital Anxiety and Depression Scale. b FSozU denotes Fragebogen zur Sozialen Unterstützung (Social Support Questionnaire).
This study proposes a 9-item shortened version of the Neck Pain and Disability Scale based on the selection of clinically relevant dimensions of neck pain and related disability. It includes aspects of neck pain intensity, problems with neck movement, neck pain effects on emotion and cognition, its interference with life activities, and the effect of pain pills. The newly developed sf-NPAD showed construct and discriminative validity when compared with clinical, psychosocial, and health care utilisation markers and it demonstrated substantial internal consistency. To increase generalisability, results from two different samples were used for development and validation of the short version. The scale development was based on patients from a hospital setting in the USA. Validity and reliability were evaluated in a general practice setting in Germany, an independent sample from a culturally and clinically different context. Several limitations should be considered. First, the scale has only been tested in a single setting. Due to the eligibility criteria of the study, persons who consulted their GP because of a new trauma due to an accident, an injury, or violence, who were terminally ill, suffered from cancer, were in need of nursing care or had severe cognitive impairment were excluded from this sample. The applicability of the scale in other clinical and research settings, and
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
generalisability to other populations of neck pain patients has to be evaluated further. Secondly, the evaluation sample demonstrates a rather large number of exclusions. However, the study was conducted in a relatively large group recruited by a defined algorithm from the whole patient population of various practices (Fig. 1), and the exclusions can be traced back to predefined reasons according to this algorithm. Thirdly, the evaluation of the newly developed scale has been done using the German translation of the NPAD, the NPAD-d (Scherer et al., 2008). Finally, the instrument has not been tested for aspects of reliability beyond internal consistency and for sensitivity to change, to detect change over time, or for feasibility and clinical utility. Further studies are needed to evaluate these properties of the measure, and to evaluate it in separate settings and language versions. This study does, however, provide a useful first step for a shortened neck pain assessment instrument. Another potential limitation is related to the factor structure of the original NPAD instrument which was used as a basis for development of the shortened instrument. Previous studies evaluating other language versions of the NPAD original version could not replicate the 4–5 factor structures as proposed by Wheeler et al. In contrast, these evaluations revealed major instability in the factor structure of the scale with frequent cross-loading or non-loading of items and with 1–3 factors extracted (Goolkasian et al., 2002; Wlodyka-Demaille et al., 2002; Cook et al., 2006; Scherer et al., 2008; Bremerich et al., 2008; Monticone et al., 2008). However, as opposed to the meaning of these statistics in research settings, psychometric analyses may not reflect all aspects that are relevant for clinical practice (Delis et al., 2003). For selection of an approach to shorten the scale we focused on clin-
864.e5
ical relevance and downgraded psychometric instabilities. The factor structure proposed by Wheeler et al. has face validity and reflects clinically relevant dimensions of neck pain and related disability. Generally, a short version can be generated in different ways (Blozik et al., 2007; Barber et al., 2005; Melzack, 1987; Bohus et al., 2009). However, if one would have focused on the absolute item-to-total scale rank order, the highly clinically relevant question about the effect of pain pills would have been missed. As for this item, we suggest to add ‘‘If you ever took pain pills for neck pain. . .”. This question revealed to have a notably higher number of missing values (Scherer et al., 2008), probably due to persons not taking pain pills who were confused. As for a missing items rule for the sf-NPAD we propose to apply the same that is used for the 20-item version (Scherer et al., 2008) which, in particular, means that no more than 15% of the sf-NPAD items should be missing. In conclusion, the 9-item sf-NPAD seems to be a valid and internally consistent abbreviation of the 20-item NPAD original version. Thus the sf-NPAD may be a useful tool in the assessment and management process of neck pain and in neck pain-related research.
Acknowledgement The study was supported by the German Ministry of Education and Research (BMBF), Grant No. 01 GK 0516. MS was funded by a Young Investigators Award of the BMBF. We are grateful to the practitioners and participants involved in this study.
1308 consulted general practitioner because of neck pain in previous 12 months
excluded: 80 did fulfil inclusion criteria 1228 invited to participate
excluded: 745 were not willing to participate
483 received questionnaire
excluded: 22 did not complete or return questionnaire 461 completed questionnaire
13 no NPAD-d score available: > 3 NPAD-d items missing 448 analytic study sample: valid NPAD-d score available Fig. 1. Flowchart of participants of the evaluation sample.
864.e6
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
References Agarwal S, Allison GT, Agarwal A, Singer KP. Reliability and validity of the Hindi version of the Neck Pain and Disability Scale in cervical radiculopathy patients. Disabil Rehabil 2006;28:1405–11. Barber MD, Walters MD, Bump RC. Short forms of two condition-specific quality-oflife questionnaires for women with pelvic floor disorders (PFDI-20 and PFIQ-7). Am J Obstet Gynecol 2005;193(1):103–13. Bicer A, Yazici A, Camdeviren H, Erdogan C. Assessment of pain and disability in patients with chronic neck pain: reliability and construct validity of the Turkish version of the Neck Pain and Disability Scale. Disabil Rehabil 2004;26:959–62. Bjelland I, Dahl AA, Haug TT, Neckelmann D. The validity of the Hospital Anxiety and Depression Scale. An updated literature review. J Psychosom Res 2002;52(2):69–77. Blozik E, Stuck AE, Niemann S, Ferrell BA, Harari D, von Renteln-Kruse W, et al. Geriatric Pain Measure short form: development and initial evaluation. J Am Geriatr Soc 2007;55:2045–50. Bohus M, Kleindienst N, Limberger MF, Stieglitz RD, Domsalla M, Chapman AL, et al. The short version of the Borderline Symptom List (BSL-23): development and initial data on psychometric properties. Psychopathology 2009;42(1):32–9. Bolton JE. Sensitivity and specificity of outcome measures in patients with neck pain: detecting clinically significant improvement. Spine 2004;29:2410–7. Bremerich FH, Grob D, Dvorak J, Mannion AF. The Neck Pain and Disability Scale: cross-cultural adaptation into German and evaluation of its psychometric properties in chronic neck pain and C1-2 fusion patients. Spine 2008;33(9):1018–27. Carroll LJ, Hogg-Johnson S, van der Velde G, Haldeman S, Holm LW, Carragee EJ, et al. Bone and Joint Decade 2000–2010 Task Force on Neck Pain and Its Associated Disorders. Course and prognostic factors for neck pain in the general population: results of the Bone and Joint Decade 2000–2010 Task Force on Neck Pain and Its Associated Disorders. Spine 2008;33(4 Suppl):S75–82. Cohen J. Statistical power analysis for the behavioral sciences. 2nd ed. New York (NY): Academic Press; 1988. Cook C, Richardson JK, Braga L, Menezes A, Soler X, Kume P, et al. Cross-cultural adaptation and validation of the Brazilian Portuguese version of the neck disability index and Neck Pain and Disability Scale. Spine 2006;31:1621–7. Cote P, Cassidy D, Carroll L. The Saskatchewan health and back pain survey: the prevalence of neck pain and related disability in Saskatchewan adults. Spine 1998;23:1689–98. Delis DC, Jacobson M, Bondi MW, Hamilton JM, Salmon DP. The myth of testing construct validity using factor analysis or correlations with normal or mixed clinical populations: lessons from memory assessment. J Int Neuropsychol Soc 2003;9:936–46. DeVellis RF. Scale development: theory and applications. 2nd ed. Newbury Park (CA): Sage; 2003. Deyo RA, Andersson G, Bombardier C, Cherkin DC, Keller RB, Lee CK, et al. Outcome measures for studying patients with low back pain. Spine 1994;19:2032S–6S. Eaker S, Bergström R, Bergström A, Adami HO, Nyren O. Response rate to mailed epidemiologic questionnaires: a population-based randomized trial of variations in design and mailing routines. Am J Epidemiol 1998;147:74–82. Frydrich T, Sommer G, Brähler E. F-SozU – Fragebogen zur Sozialen Unterstützung. In: Brähler E, Schumacher J, Strauß B, editors. Diagnostische Verfahren in der Psychotherapie. Göttingen: Hogrefe; 2002. Goolkasian P, Wheeler AH, Gretz SS. The Neck Pain and Disability Scale: test–retest reliability and construct validity. Clin J Pain 2002;18:245–50. Herrmann C. International experiences with the Hospital Anxiety and Depression Scale – a review of validation data and clinical results. J Psychosom Res 1997;42(1):17–41.
Herrmann CH, Buss U, Snaith RP. HADS-D – Hospital Anxiety and Depression ScaleDeutsche Version: Ein Fragebogen zur Erfassung von Angst und Depressivität in der somatischen Medizin. Bern: Hans Huber; 1995. Jordan A, Manniche C, Mosdal C, Hindsberger C. The Copenhagen Neck Functional Disability Scale: a study of reliability and validity. J Manipul Physiol Ther 1998;21:520–7. Kongsted A, Bendix T, Qerama E, Kasch H, Bach FW, Korsholm L, et al. Acute stress response and recovery after whiplash injuries. A one-year prospective study. Eur J Pain 2008;12:455–63. Kose G, Hepguler S, Atamaz F, Oder G. A comparison of four disability scales for Turkish patients with neck pain. J Rehabil Med. 2007;39:358–62. Leak AM, Cooper J, Dyer S, Williams KA, Turner-Stokes L, Frank AO. The Northwick park Neck Pain Questionnaire, devised to measure neck pain and disability. Br J Rheumatol 1994;33:469–74. Lee H, Nicholson LL, Adams RD, Maher CG, Halaki M, Bae SS. Development and psychometric testing of Korean language versions of 4 neck pain and disability questionnaires. Spine 2006;31:1841–5. Melzack R. The short-form McGill Pain Questionnaire. Pain 1987;30(2):191–7. Monticone M, Baiardi P, Nido N, Righini C, Tomba A, Giovanazzi E. Development of the Italian version of the Neck Pain and Disability Scale, NPDS-I: cross-cultural adaptation, reliability, and validity. Spine 2008;33:E429–34. Mousavi SJ, Parnianpour M, Montazeri A, Mehdian H, Karimi A, Abedi M, et al. Translation and validation study of the Iranian versions of the neck disability index and the Neck Pain and Disability Scale. Spine 2007;32: E825–31. Nunnally JC, Bernstein IH. Psychometric theory. 3rd ed. New York (NY): McGraw Hill; 1994. Pietrobon R, Coeytaux RR, Carey S, et al. Standard scales for measurement of functional outcome for cervical pain or dysfunction. A systematic review. Spine 2002;27:515–22. Resnick DN. Subjective outcome assessments for cervical spine pathology: a narrative review. J Chiropr Med 2005;4:113–34. Scherer M, Blozik E, Himmel W, Laptinskaya D, Kochen MM, Herrmann-Lingen C. Psychometric properties of a German version of the Neck Pain and Disability Scale. Eur Spine J 2008;17:922–9. Streiner DJ, Norman GR. Health measurement scales: a practical guide to their development and use. 2nd ed. Oxford: Oxford University Press; 1995. Vernon H, Mior S. The neck disability index: a study of reliability and validity. J Manipul Physiol Ther 1991;14:409–15. Westaway MD, Stratford PW, Binkley JM. The patient-specific functional scale: validation of its use in persons with neck dysfunction. J Orthop Sports Phys Ther 1998;27:331–8. Wetzel D, Himmel W, Heidenreich R, Hummers-Pradier E, Kochen MM, Rogausch A, et al. Participation in a quality of care study and consequences for generalizability of general practice research. Fam Pract 2005;22:458–64. Wheeler AH, Goolkasian P, Baird AC, Darden 2nd BV. Development of the Neck Pain and Disability Scale. Item analysis, face, and criterion-related validity. Spine 1999;24:1290–4. Wlodyka-Demaille S, Poiraudeau S, Catanzariti JF, Rannou F, Fermanian J, Revel M. French translation and validation of 3 functional disability scales for neck pain. Arch Phys Med Rehabil 2002;83:376–82. Wlodyka-Demaille S, Poiraudeau S, Catanzariti JF, Rannou F, Fermanian J, Revel M. The ability to change of three questionnaires for neck pain. Joint Bone Spine 2004;71:317–26. Wlodyka-Demaille S, Poiraudeau S, Fermanian J, Catanzariti JF, Rannou F, Revel M. French translation and validation of a functional disability scale for neck pain. Ann Readapt Med Phys 2001;44:132–42. Zigmond AS, Snaith RP. The Hospital Anxiety and Depression Scale. Acta Psychiat Scand 1983;67(6):361–70.
E. Blozik et al. / European Journal of Pain 14 (2010) 864.e1–864.e7
864.e7
Appendix 1 Items and scoring rules of Neck Pain and Disability Scale original version (NPAD) and Neck Pain and Disability Scale short form (sf-NPAD). 1. How bad is your pain today? No pain
│___0___│___1___│___2___│___3___│___4___│___5___│ Most severe pain
2. How bad is your pain on the average? No pain
│___0___│___1___│___2___│___3___│___4___│___5___│ Most severe pain
3. How bad is your pain at its worst? No pain
│___0___│___1___│___2___│___3___│___4___│___5___│ Cannot tolerate
4. Does your pain interfere with your sleep? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Can’t sleep
5. How bad is your pain with standing? No pain
│___0___│___1___│___2___│___3___│___4___│___5___│ Most severe pain
6. How bad is your pain with walking? No pain
│___0___│___1___│___2___│___3___│___4___│___5___│ Most severe pain
7. Does your pain interfere with driving or riding a car? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Can’t drive or ride
8. Does your pain interfere with social activities? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Always
9. Does your pain interfere with recreational activities? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Always
10. Does your pain interfere with work activities? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Can’t work
11. Does your pain interfere with your personal care (eating, bathing, dressing, etc)? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Always
12. Does your pain interfere with your personal relationships (family, friends, sex, etc)? Not at all
│___0___│___1___│___2___│___3___│___4___│___5___│ Always
13. How has your pain changed your outlook on life and the future (depression, hopelessness)? No change│___0___│___1___│___2___│___3___│___4___│___5___│ Complete change
14. Does pain affect your emotions? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Completely
15. Does your pain affect your ability to think or concentrate? Not at all │___0___│___1___│___2___│___3___│___4___│___5___│ Completely
16. How stiff is your neck? Not stiff
│___0___│___1___│___2___│___3___│___4___│___5___│ Can’t move neck
17. How much trouble do you have turning your neck? No trouble│___0___│___1___│___2___│___3___│___4___│___5___│ Can’t move neck
18. How much trouble do you have looking up or down? No trouble │___0___│___1___│___2___│___3___│___4___│___5___│ Can’t look up or down
19. How much trouble do you have working overhead? No trouble │___0___│___1___│___2___│___3___│___4___│___5___│Can´t work overhead
20. How much do pain pills help? Complete relief │___0___│___1___│___2___│___3___│___4___│___5___│ No relief
Items included in sf-NPAD are marked in light grey. Calculation of NPAD original score: total score (0–100) = sum of all items (0–5). Calculation of sf-NPAD score: total score (0–45) = sum of all items (0–5); transformation to a 0–100 scale by multiplying the raw total score by 20/9.