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Psychometric properties of Aquarel
Journal of Clinical Epidemiology 54 (2001) 157–165
Psychometric properties of Aquarel: a disease-specific quality of life questionnaire for pacemaker patients Monique A. M. Stofmeela,b,c, Marcel W. M. Postb,d, Johannes C. Kelderc, Diederick E. Grobbeeb, Norbert M. van Hemelc,* a Heart Lung Centre, Utrecht, The Netherlands Julius Centre for Patient Oriented Research, University Hospital, Utrecht, The Netherlands c Department of Cardiology, St. Antonius Hospital, Koekoekslaan 1, 3435 CM, Nieuwegein, The Netherlands d Institute for Rehabilitation Research, Hoensbroek, The Netherlands Received 8 September 1999, received in revised form 7 April 2000; accepted 5 May 2000 b
Abstract In cardiac pacing current clinical practice permits the use of ventricular or atrioventricular-synchronous pacemakers. However, it is not known which type of pacemaker results in superior clinical and patient outcomes. To date, there is no feasible and validated disease-specific questionnaire for pacemaker patients to assess quality of life (QoL) available. The Aquarel questionnaire was developed as a diseasespecific extension to the Short-Form-36 (SF-36). A cross-sectional study was carried out in 74 pacemaker patients to evaluate validity and reliability of this instrument. Items were selected and scales constructed based on factorial analysis. Internal consistency, content validity and test–retest reliability were moderate to excellent. Correlations with the SF-36 scales, pacing mode and functional tests were as hypothesized, demonstrating the individual value and distinctiveness of the Aquarel subscales. The results support the feasibility and usefulness of evaluating QoL in pacemaker patients when using Aquarel as an extension to the SF-36. © 2001 Elsevier Science Inc. All rights reserved. Keywords: Quality of life; Questionnaires; Cardiac pacing; Artificial
1. Introduction Quality of life (QoL) is an important outcome of clinical management and research trials, covering the functional, psychological, cognitive, and social aspects of living. Several generic QoL questionnaires have been developed over the past decades. However, these instruments are often insufficient in patients with typical symptoms due to the disease under study. Many different disease-specific QoL scales have therefore been developed to sensitively and reliably measure disease-specific aspects [1]. The introduction of atrioventricular-synchronous pacemakers (DDD/R and AAI/R) and ventricular rate adaptive pacemakers (VVIR) showed improved hemodynamics, exercise capacity and a lower cost-effectiveness ratio compared to the original fixed rate ventricular pacemakers (VVI) [2–15]. The benefits of DDDR over VVIR are less clear. Nevertheless, the accompanying rise in costs will be enormous when physiological pacing is used according to the guidelines of the British Pacing and Electrophysiology * Corresponding author. Tel: ⫹31-30-6093366, fax: ⫹31-306034420. E-mail address: [email protected] (N.M. van Hemel)
Group [16]. Therefore, QoL might be a valuable additive parameter to exercise capacity for a proper evaluation of pacing therapy. Although several pacing studies used QoL questionnaires, none of these questionnaires had been formally validated and QoL results were conflicting or at best subtle. So the findings of these studies should be interpreted cautiously [17]. Especially because of the subtle differences in symptomatology between subgroups of pacemaker patients, use of a disease-specific instrument is important for the measurement of QoL, and addition of a disease-specific questionnaire to a well-known and thoroughly validated generic questionnaire will incorporate the advantages of both approaches [18]. The Karolinska QoL questionnaire is currently the only disease-specific QoL questionnaire for which there is supportive evidence of validity [19]. It is a questionnaire composed from a selection of previously developed questionnaires to which questions on cardiovascular symptomatology were added. It consists of 94 items on seven dimensions (cardiovascular symptoms, physical functioning and sleep, emotional functioning, cognitive functioning, social functioning, self-perceived health and life events). A score is computed for each dimension separately. Linde et al. [18]
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demonstrated a difference in QoL in favour of some symptom scales, but no data on content or construct validity are presented. Gadler et al. [19] showed moderate correlations of the symptoms and activity scales of this questionnaire with NYHA classification, but information on correlations of the remaining scales with NYHA classification are not presented. These facts limit the value of these validation data. In our opinion, the Karolinska QoL questionnaire is rather long and its time consuming to score because of the use of many visual analogue scales. Moreover, several scales concern topics that are relevant aspects of QoL, but are not specific for pacemaker patients. We preferred to use a truly generic questionnaire for these aspects to facilitate comparisons with other diagnostic groups [20]. Therefore, the aim of this study was to compose a feasible, self-administered, disease-specific questionnaire for pacemaker patients and to examine the psychometric properties of this instrument. The scale structures, their reliability and the content validity were determined.
2. Methods 2.1. Questionnaire development The Aquarel questionnaire (Assessment of QUality of life And RELated events) was designed as a pacemaker-specific extension of the SF-36, with the same time frame of 4 weeks. The SF-36 was chosen as the core module because it is well appreciated for its psychometric properties and widely used in several medical disciplines including cardiology [14,21–27]. It contains the minimum set of domains that should be evaluated to get a good impression of the QoL of an adult person [28]. Furthermore, it is easy to administrate and takes little time to fill out. For the Aquarel questionnaire 27 items were designed or selected from previously developed questionnaires. The questions of cardiovascular symptomatology were adapted from the Karolinska QoL Questionnaire [15]. New questions were added about palpitations, dyspnea and tiredness. We used this version in semistructured interviews with eight patients with a history of pacemaker implantation, to judge whether according to the experience of particularly articulate and/or disabled patients items were missing or superfluous [29]. Selection of the interviewed patients was based upon age, sex, indication for pacemaker implantation, time passed since pacemaker implantation and type of pacemaker implanted. For the preliminary version the original English items from the existing questionnaires were translated by someone who is not only fluent in both languages, but who also has knowledge of the content area, and was aware of the intent of each item and of the scale as a whole. The reason for this procedure was that the literal translation of phrases may convey very different meanings in the two languages; feelings, disorders and even symptoms may not be expressed in the same manner in different cultures. The next step was
‘back-translation.’ A different bilingual person, who was not associated with the translation phase and again had some knowledge of the content area, translated the new Dutch version into the original language. If the meaning seemed to have been lost or altered, the item went through the process again [30,31]. 2.2. Patient population and administration A cross-sectional study was carried out from October 1998 until April 1999 at the outpatient clinic of the St. Antonius Hospital, Nieuwegein, a tertiary referral and teaching hospital in the Netherlands. Patients over 18 years of age, male or female, whose clinical condition had been stable for at least 6 months were invited to participate. Patients were excluded when there was inadequate knowledge of the Dutch language for self-administration of the questionnaire, physical inability to perform a 6-min walking test or serious disease at the time of inclusion. After written informed consent was obtained, patients were asked to complete a selfadministered questionnaire and to perform a 6-min walking test, which is preferable to other exercise testing because of its better acceptance and feasibility [32]. The consulting cardiologist registered the functional status according to the NYHA classification and scheduled an appointment for echocardiography if this had not been performed during the previous 6 months. Patients who agreed to participate were asked to fill out the questionnaire at home for a second time after a period of 2 weeks and to mail it back in a prepaid envelope. If questionnaires were incomplete, patients were contacted by telephone for additional answers. 2.3. Scoring Each item on the questionnaire was to be answered in Likert format of five categories. Patients were instructed to answer all questions by putting a sign in front of the most appropriate answer. The written introduction to the questionnaire made it clear that there were no right or wrong answers and that all items needed to be completed. The score was reversed on certain items so that a high score consistently represented a better QoL. Sumscores were calculated for all scales identified with factor analysis and transformed, to obtain values ranging from 0 to 100 with 100 representing perfect QoL. This might not be the best way to reflect QoL; however, it is in agreement with the methods used in scoring the SF-36, and therefore the easiest to interpret by the reader. 2.4. Analysis The responses to the questionnaire were subjected to recommended tests of reliability and validity [1,33,34]. Psychometric properties of the Aquarel questionnaire were analysed in six ways: (1) The individual items were subjected to factorial analysis using varimax rotation in the SPSS (Statistical Package for the Social Sciences) Factor Analysis program, to simplify the overall structure [35]; (2)
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internal consistency of the obtained scales was evaluated using Cronbach’s alpha; (3) confirmation of the scale structure was assessed by obtaining correlations between scales using Pearson correlation coefficient; (4) content validity was analysed through the correlations of the specific scales to the SF-36, NYHA classification, echocardiographic findings and results of the 6-min walking test; (5) test–retest reliability was evaluated by intraclass correlations (ICC) calculated on data produced from one-way analysis of variance [36] and (6) by the Bland and Altman method on Aquarel items selected for the preliminary version of the questionnaire [37]. ICC analyses were specifically designed to examine reliability, providing a reliability index to indicate the measurement error. Bland and Altman’s method assesses agreement between clinical measurements, based on analysis of differences between measurements. This combination of tests was done because neither test alone provides sufficient information. 3. Results 3.1. Patient characteristics Seventy-four patients were included. Table 1 summarizes the demographic and clinical characteristics together with the response rates. The overall proportion of returned second questionnaires was high for a postal survey (98.7%) [38,39]. The distribution of age, sex, NYHA classification and pacing modes is representative for patient populations at outpatient clinics in the Netherlands [40]. 3.2. Factor analysis A first factor analysis extracted seven factors or subgroups of items containing interrelated information on the Aquarel questionnaire, based on eigenvalues larger than 1.0, which is the criterion used by rule [34]. The fifth subgroup clearly represented cognitive functioning (items 18–21, see the Appendix), but no clear subscales on disease-specific complaints could be identified. When the items on cognition were left out and a second factor analysis was done, three additional subscales could be composed (Table 2). Responses to questions 7–10 (dyspnea on exertion) and 22–24 (fatigue) were highly interrelated, and could be labelled as a physical dimension. Questions 1–6 (chest pain) and 11–12 (dyspnea at rest) formed a second subgroup that was labelled as chest discomfort. The third subgroup contained interrelated items 13–17 and was labelled as arrhythmias. With the second factor analysis three problematic items (25–27) were identified and therefore discarded from the final version of the questionnaire. 3.3. Distribution of scores and internal consistency of scales Both are presented in Table 3. The mean scores on each scale were between 60 and 90, indicating a moderate impact of pacemaker therapy on QoL. The mean scores did not dif-
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Table 1 Sociodemographic and clinical characteristics of the patients (n⫽74) Response rate (%) Age (mean ⫾ S.D.) Sex (number and % of men) Marital status (%) Married or cohabiting Single Divorced Widow Level of education (%) Primary education Secondary education University education Occupation (%) Retired Full time job Housewife Disability Unemployed Cardiovascular medication (%) Antiarrhythmic drugs ACE inhibitors Digoxin Pacing mode (%) DDDR DDD VVIR VVI AAIR AAI Years since first implant (mean ⫾ S.D.) NYHA classification (%) Class I Class II Class III Class IV Indication for PM implantation (%) Atrioventricular block Sinus node disease Bradytachy syndrome Atrial fibrillation with slow ventricular rate
98.7 65.9 ⫾ 13 47 (63.5) 82.4 5.4 2.7 9.5 29.7 51.4 19.0 45.9 12.2 17.6 21.6 1.4 35.1 41.9 16.2 23.0 10.8 43.2 14.9 1.4 2.7 8.6 ⫾ 6.2 32.4 48.6 18.9 — 70 15.7 8.6 5.7
fer too much from the median values and visual inspection of the distribution of scores revealed a quite normal distribution. Internal consistency was assessed with Cronbach’s alpha coefficient. It has been suggested that a coefficient of ⬎0.5 is acceptable, although ideally scores should be ⭓0.7 [41]. All of the identified subscales met the last criterium. Since alpha values are generally lower for domains containing very few statements these results are indeed satisfying. 3.4. Content validity For measurements of QoL gold standards do not exist and therefore validity testing is challenging. Construct validation begins with a conceptual definition of the topic to be measured, indicating the theoretical relationship of scale scores to external criteria, such as other health measurement scales or other methods that measure the same concept [1]. An example is the correlation of 6-min walking distance with the score on the dimension physical functioning. The hypothesis put forward was that patients with short 6-min
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Table 2 Disease-specific dimensions of the Aquarel questionnaire based on a second factor analysis Factor 1 Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Item 7 Item 8 Item 9 Item 10 Item 11 Item 12 Item 13 Item 14 Item 15 Item 16 Item 17 Item 22 Item 23 Item 24 Item 25 Item 26 Item 27
Factor 2
.303
Factor 3
.609 .838 .721 .669 .826 .761
.838 .828 .803 .809 .369 .304 .335
.304
.591 .572
.341 .600 .687 .631 .626 .628
.314
.541 .640 .693 .354 .493
⫺.331 .423
.468 .303
Values lower then .3 are suppressed.
walking distance, a lower NYHA classification or ventricular pacing would have a lower QoL score, and that left ventricular end diastolic diameter would not correlate with QoL scores. Furthermore, a small to moderate correlation was expected with the SF-36. The correlation between comparable dimensions should be higher than the correlations between less comparable dimensions. The expected relations were generally observed (Table 4). Moderate correlations between the dimensions of the Aquarel and the SF-36 were found. Comparison of mean scores between patients according to pacing mode, 6-min walk distance and NYHA classification revealed significant differences as demonstrated in Table 5. There was a negative correlation of the QoL scores with NYHA classification (higher classification related to worse QoL) and a positive correlation with the results of 6-min walking test. Furthermore, QoL scores were in favour
of dual chamber pacing. These findings are an indication for construct validity. 3.5. Test–retest reliability In trials, QoL scores must have a high reliability when a condition is stable in order to be confident that changes in scores are related to treatment. Test–retest reliability calculations revealed that the Aquarel QoL questionnaire was stable upon repeated administration from baseline to 1–2 weeks. The correlation coefficients between first and second measurement varied from 0.79 to 0.92, indicating a good degree of association between the test and retest scores. ICCs were moderate to excellent for all scales (0.80 to 0.91), thereby exceeding 0.70 as the acceptable value for group comparisons in clinical studies [34]. However, these values do not indicate the direction of the association and therefore repeatability was also assessed by the method recommended by Bland and Altman [37]. The differences between two measurements (with a 1–2week interval) were plotted against the overall mean of the two measurements. The variance of the differences was calculated and 95% confidence intervals (CI) constructed. Patients with the same values for average and difference in scores were represented by SPSS as one dot. All dots outside the 95% CI were therefore checked and appeared to represent a single case. So there appeared to be no relation between the difference and the mean (Fig. 1), demonstrating a constant level of error, independent of the value of the mean. The dots outside the 95% CIs are not on one side, indicating that scores on the second questionnaire were not systematically higher or lower with repeated administration. The mean of the differences was not statistically significantly different from zero, indicating that there is no systematic error.
4. Discussion Over the past decades there has been a rapid development of highly sophisticated pacing devices and an increasing
Table 3 Score distribution and scales reliability
Questionnaire 1 Cognitive functioning Chest discomfort Dyspnea on exertion Arrhythmias Questionnaire 2 Cognitive functioning Chest discomfort Dyspnea on exertion Arrhythmias
n
Means of scores
Medians of scores
S.D.
Cronbach’s ␣
74 74 74 74
69.00 85.29 64.03 80.95
68.75 90.63 60.71 85.00
19.86 15.48 20.38 16.40
.75 .89 .90 .73
73 73 73 73
68.15 86.14 65.24 79.79
68.75 90.63 61.29 80.00
21.22 13.15 21.21 17.25
.81 .83 .92 .74
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Table 4 Multidimensional matrix of Pearson correlation coefficients for Aquarel and SF-36 Aquarel
Aquarel: Cognition Chest discomfort Dyspnea & exertion Arrhythmias SF-36: Physical functioning Social functioning Role functioning (phys.) Role functioning (emo.) Mental health Vitality Pain General health
Cognition
Chest discomfort
Dyspnea & exertion
.43 .53 .46
.54 .47
.45
.42 .58 .31 .27 .49 .39 .36 .49
.47 .41 .36 .37 .48 .40 .63 .61
.83 .52 .69 .46 .46 .69 .60 .78
Arrhythmias
.36 .42 .31 .23 .46 .38 .38 .46
naires and the conflicting results [7,14], the value of the QoL results obtained can be questioned. To prevent noncomparable pacing reports it is desirable to have a standard questionnaire for evaluation of QoL. The purpose of this study was to assess the characteristics and feasibility of a new self-administered QoL questionnaire, designed for pacemaker patients specifically “Aquarel.” The psychometric properties (validity and reliability) of this questionnaire were found satisfactory and suggest this instrument to be valid and reliable. The inter scale correlations within the Aquarel questionnaire as well as with the SF-36 were moderate, demonstrating their individual value and distinctiveness. As hypothesised, the highest correlations with the SF-36 were found between comparable dimensions. Two subscales (cognition and arrhythmias) of the Aquarel appeared to perform quite poorly (Table 5). This
number of indications for implant [42]. Since age at first implant is about 75 years and exercise capacity generally low, the question remains whether implantation of expensive pacemakers and the associated escalating costs are justified. Therefore, the evaluation of proper pacemaker therapy should not merely be based on clinical outcomes like maximal exercise capacity, but on an assessment of QoL as well. Stofmeel et al. [20] performed a review of the literature on this topic. Fourteen studies using multi-item questionnaires for evaluating QoL in DDD pacing compared to VVI(R) pacing were selected for review. Most of the studies showed improved QoL of dual-chamber pacing compared to ventricular pacing (with, as well as without, rate adaptation). Differences in QoL scores were nonsignificant in several studies and most other studies did not show consistent QoL effects in all scales used. In view of the fact that only two studies used validated (nondisease-specific) question-
Table 5 Mean scores according to pacing mode, 6-min walk test and NYHA classification Pacing mode
SF-36 Physical functioning Social functioning Role functioning (phys.) Role functioning (emo.) Mental health Vitality Pain General health Aquarel Cognition Chest discomfort Dyspnea & exertion Arrhythmias
6-min-walktest
NYHA
Atrial/dual (n⫽43)
Ventricular (n⫽28)
⬍375 mtr (n⫽27)
⭓375 mtr (n⫽47)
I (n⫽24)
II (n⫽36)
III (n⫽14)
73.13 87.95 61.61 71.43 76.71 70.77 86.88 66.81
54.02* 75.00* 45.35 68.99 69.42 57.44* 73.37* 51.79*
40.00 72.22 25.93 49.38 67.56 51.67 64.17 44.76
72.78* 82.45 67.02* 80.14* 74.23 68.87* 87.45* 65.22*
82.94 89.06 81.25 86.11 80.71 77.78 90.05 74.57
55.56 75.69 41.67 62.04 64.00 55.97 77.10 53.68
36.43* 68.75* 28.75* 57.14* 76.57* 53.57* 64.72* 40.71*
74.55 90.29 73.72 84.11
65.99 82.02* 57.70* 78.14
67.36 78.54 50.55 76.30
69.95 89.16* 71.78* 83.62
73.44 92.19 80.36 86.25
69.10 82.99 59.78 77.78
61.16 79.37* 46.98* 80.00
* P value of independent T test or one-way-ANOVA ⬍0.05.
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Fig. 1. Difference against average scores on Aquarel subscales.
result can be explained by the fact that the studied group of patients had a pacemaker implanted since 8.6 (mean) years. The added value of these two subscales of the Aquarel is likely to be put forward when looking at patients before and after primo implantation of a pacemaker. Therefore, these scales are not omitted from the Aquarel questionnaire for the time being. This study has a number of limitations. First, only 74 subjects were studied. This number of subjects was sufficient to demonstrate psychometric properties, but a larger group of patients would test its performance more firmly, especially the factor analysis. Secondly, repeatability was very acceptable on group level as demonstrated with different techniques, but it should be recognised that the difference between test and retest without a significant change in health can rise up to about 20 points (Fig. 1), which limits the usefulness of this instrument for evaluation of QoL in individual patients. To determine which change in score represents an important change in health, a larger number of patients needs to be evaluated in a longitudinal designed
study. Thirdly, sex and age were unequally distributed among the subgroups within pacing mode, 6-min walk test and NYHA. However, multivariate analyses including sex and age did not materially affect the results (data not shown). Finally, the Aquarel QoL questionnaire was tested in one institution only. 5. Conclusion This study has demonstrated the feasibility and usefulness of a self-administered QoL questionnaire for pacemaker patients, when added to the SF-36. Depending on the results of ongoing research into its responsiveness to change, and whether it is judged that the cost of collecting this information is justified, the Aquarel questionnaire may well prove to be an outcome measure suitable for use in studies with pacemaker patients. Results obtained in this validation study are promising and we anticipate to corroborate these results in further studies using the Aquarel questionnaire.
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Appendix. Preliminary version of Aquarel 1. Have you felt discomfort in the chest? ⵧ no discomfort at all ⵧ very mild discomfort ⵧ mild discomfort ⵧ moderate discomfort ⵧ great discomfort 2. Do you get chest discomfort while walking upstairs or uphill? ⵧ no discomfort ⵧ very mild discomfort ⵧ mild discomfort ⵧ moderate discomfort ⵧ severe discomfort 3. Do you get chest discomfort while walking quickly on level ground? ⵧ no discomfort ⵧ very mild discomfort ⵧ mild discomfort ⵧ moderate discomfort ⵧ severe discomfort 4. Do you get chest discomfort while walking on level ground at the same pace as people usually do at your age? ⵧ no discomfort ⵧ very mild discomfort ⵧ mild discomfort ⵧ moderate discomfort ⵧ severe discomfort 5. Have you been restricted by chest discomfort during physical exercise? ⵧ not restricted at all ⵧ slightly restricted ⵧ moderately restricted ⵧ very restricted ⵧ extremely restricted 6. Have you experienced chest discomfort at rest? ⵧ no discomfort ⵧ very mild discomfort ⵧ mild discomfort ⵧ moderate discomfort ⵧ severe discomfort 7. Do you get short of breath while walking upstairs or uphill? ⵧ not short of breath ⵧ very mildly short of breath ⵧ mild short of breath ⵧ moderate short of breath ⵧ extreme short of breath 8. Do you get short of breath while walking quickly on level ground? ⵧ not short of breath ⵧ very mildly short of breath ⵧ mild short of breath ⵧ moderate short of breath
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ⵧ extreme short of breath 9. Do you get short of breath while walking on level ground at the same pace as people usually do at your age? ⵧ not short of breath ⵧ very mildly short of breath ⵧ mild short of breath ⵧ moderate short of breath ⵧ extreme short of breath 10. Have you been restricted by breathlessness during physical exercise? ⵧ not restricted at all ⵧ slightly restricted ⵧ moderately restricted ⵧ very restricted ⵧ extremely restricted 11. Have you been out of breath at rest? ⵧ not out of breath ⵧ slightly out of breath ⵧ moderately out of breath ⵧ very out of breath ⵧ extremely out of breath 12. Do you awake when sleeping due to shortness of breath? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 13. Did you have swollen ankles? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 14. Have you suffered from an irregular heartbeat? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 15. Have you suffered from heart pounding? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 16. Have you suffered from pounding in the neck or abdomen? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 17. Have you felt close to fainting?
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ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 18. Have you had trouble in making up your mind? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 19. Have you had trouble with remembering things? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 20. Have you had difficulty in concentration? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 21. Have you had trouble falling asleep? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 22. Do you feel tired and exhausted after a night’s sleep? ⵧ never ⵧ seldom ⵧ once in a while ⵧ often ⵧ continuously 23. Have you been restricted in your daily activities due to tiredness or lack of energy? ⵧ extremely restricted ⵧ very restricted ⵧ moderately restricted ⵧ slightly restricted ⵧ not restricted at all 24. Do you have to sit or lie down during the day to rest? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously
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[33] Streiner DI, Norman GR. Health measurements scales; a practical guide to their development and use. New York: Oxford University Press, 1991. [34] Staquet MJ, Hays RD, Fayers PM. Quality of life assessments in clinical trials. New York: Oxford University Press, 1998. [35] Norusis MJ. SPSS 8.0 guide to data analysis. Englewood Cliffs, NJ: Prentice-Halle Inc., 1998. [36] Rankin G, Stokes M, Reliability of assessment tools in rehabilitation: an illustration of appropriate statistical analyses. Clin Rehabil 1998; 12:187–99. [37] Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;1:307–10. [38] Hoffman SC, Burke AE, Helzlsouer KJ, Comstock GW. Controlled trial of the effect of length, incentives, and follow-up techniques on response to a mailed questionnaire. Am J Epidemiol 1998;148:1007–11. [39] Mallinson S. The Short-Form 36 and older people: some problems encountered when using postal administration. J Epidemiol Community Health 1998;52:324–8. [40] Ector H, Feruglio GA. Cardiac pacing in Europe: Anno 1993. In: Hemel van NM. Wittkampf FHM, Ector H, editors. The pacemaker clinic of the 90’s; essentials in brady-pacing, 1st ed. Dordrecht: Kluwer Academic Publishers, 1995. pp. 227–37. [41] Jenkinson C, Wright L, Coulter A. Criterion validity and reliability of the SF-36 in a population sample. Qual Life Res 1994;3:7–12. [42] Dreifus LS, Fisch C, Griffin JC, Gillette PC, Mason JW, Parsonnet V. Guidelines for implantation of cardiac pacemakers and antiarrhythmia devices. JACC 1991;18:1–13.
Psychometric properties of Aquarel: a disease-specific quality of life questionnaire for pacemaker patients Monique A. M. Stofmeela,b,c, Marcel W. M. Postb,d, Johannes C. Kelderc, Diederick E. Grobbeeb, Norbert M. van Hemelc,* a Heart Lung Centre, Utrecht, The Netherlands Julius Centre for Patient Oriented Research, University Hospital, Utrecht, The Netherlands c Department of Cardiology, St. Antonius Hospital, Koekoekslaan 1, 3435 CM, Nieuwegein, The Netherlands d Institute for Rehabilitation Research, Hoensbroek, The Netherlands Received 8 September 1999, received in revised form 7 April 2000; accepted 5 May 2000 b
Abstract In cardiac pacing current clinical practice permits the use of ventricular or atrioventricular-synchronous pacemakers. However, it is not known which type of pacemaker results in superior clinical and patient outcomes. To date, there is no feasible and validated disease-specific questionnaire for pacemaker patients to assess quality of life (QoL) available. The Aquarel questionnaire was developed as a diseasespecific extension to the Short-Form-36 (SF-36). A cross-sectional study was carried out in 74 pacemaker patients to evaluate validity and reliability of this instrument. Items were selected and scales constructed based on factorial analysis. Internal consistency, content validity and test–retest reliability were moderate to excellent. Correlations with the SF-36 scales, pacing mode and functional tests were as hypothesized, demonstrating the individual value and distinctiveness of the Aquarel subscales. The results support the feasibility and usefulness of evaluating QoL in pacemaker patients when using Aquarel as an extension to the SF-36. © 2001 Elsevier Science Inc. All rights reserved. Keywords: Quality of life; Questionnaires; Cardiac pacing; Artificial
1. Introduction Quality of life (QoL) is an important outcome of clinical management and research trials, covering the functional, psychological, cognitive, and social aspects of living. Several generic QoL questionnaires have been developed over the past decades. However, these instruments are often insufficient in patients with typical symptoms due to the disease under study. Many different disease-specific QoL scales have therefore been developed to sensitively and reliably measure disease-specific aspects [1]. The introduction of atrioventricular-synchronous pacemakers (DDD/R and AAI/R) and ventricular rate adaptive pacemakers (VVIR) showed improved hemodynamics, exercise capacity and a lower cost-effectiveness ratio compared to the original fixed rate ventricular pacemakers (VVI) [2–15]. The benefits of DDDR over VVIR are less clear. Nevertheless, the accompanying rise in costs will be enormous when physiological pacing is used according to the guidelines of the British Pacing and Electrophysiology * Corresponding author. Tel: ⫹31-30-6093366, fax: ⫹31-306034420. E-mail address: [email protected] (N.M. van Hemel)
Group [16]. Therefore, QoL might be a valuable additive parameter to exercise capacity for a proper evaluation of pacing therapy. Although several pacing studies used QoL questionnaires, none of these questionnaires had been formally validated and QoL results were conflicting or at best subtle. So the findings of these studies should be interpreted cautiously [17]. Especially because of the subtle differences in symptomatology between subgroups of pacemaker patients, use of a disease-specific instrument is important for the measurement of QoL, and addition of a disease-specific questionnaire to a well-known and thoroughly validated generic questionnaire will incorporate the advantages of both approaches [18]. The Karolinska QoL questionnaire is currently the only disease-specific QoL questionnaire for which there is supportive evidence of validity [19]. It is a questionnaire composed from a selection of previously developed questionnaires to which questions on cardiovascular symptomatology were added. It consists of 94 items on seven dimensions (cardiovascular symptoms, physical functioning and sleep, emotional functioning, cognitive functioning, social functioning, self-perceived health and life events). A score is computed for each dimension separately. Linde et al. [18]
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demonstrated a difference in QoL in favour of some symptom scales, but no data on content or construct validity are presented. Gadler et al. [19] showed moderate correlations of the symptoms and activity scales of this questionnaire with NYHA classification, but information on correlations of the remaining scales with NYHA classification are not presented. These facts limit the value of these validation data. In our opinion, the Karolinska QoL questionnaire is rather long and its time consuming to score because of the use of many visual analogue scales. Moreover, several scales concern topics that are relevant aspects of QoL, but are not specific for pacemaker patients. We preferred to use a truly generic questionnaire for these aspects to facilitate comparisons with other diagnostic groups [20]. Therefore, the aim of this study was to compose a feasible, self-administered, disease-specific questionnaire for pacemaker patients and to examine the psychometric properties of this instrument. The scale structures, their reliability and the content validity were determined.
2. Methods 2.1. Questionnaire development The Aquarel questionnaire (Assessment of QUality of life And RELated events) was designed as a pacemaker-specific extension of the SF-36, with the same time frame of 4 weeks. The SF-36 was chosen as the core module because it is well appreciated for its psychometric properties and widely used in several medical disciplines including cardiology [14,21–27]. It contains the minimum set of domains that should be evaluated to get a good impression of the QoL of an adult person [28]. Furthermore, it is easy to administrate and takes little time to fill out. For the Aquarel questionnaire 27 items were designed or selected from previously developed questionnaires. The questions of cardiovascular symptomatology were adapted from the Karolinska QoL Questionnaire [15]. New questions were added about palpitations, dyspnea and tiredness. We used this version in semistructured interviews with eight patients with a history of pacemaker implantation, to judge whether according to the experience of particularly articulate and/or disabled patients items were missing or superfluous [29]. Selection of the interviewed patients was based upon age, sex, indication for pacemaker implantation, time passed since pacemaker implantation and type of pacemaker implanted. For the preliminary version the original English items from the existing questionnaires were translated by someone who is not only fluent in both languages, but who also has knowledge of the content area, and was aware of the intent of each item and of the scale as a whole. The reason for this procedure was that the literal translation of phrases may convey very different meanings in the two languages; feelings, disorders and even symptoms may not be expressed in the same manner in different cultures. The next step was
‘back-translation.’ A different bilingual person, who was not associated with the translation phase and again had some knowledge of the content area, translated the new Dutch version into the original language. If the meaning seemed to have been lost or altered, the item went through the process again [30,31]. 2.2. Patient population and administration A cross-sectional study was carried out from October 1998 until April 1999 at the outpatient clinic of the St. Antonius Hospital, Nieuwegein, a tertiary referral and teaching hospital in the Netherlands. Patients over 18 years of age, male or female, whose clinical condition had been stable for at least 6 months were invited to participate. Patients were excluded when there was inadequate knowledge of the Dutch language for self-administration of the questionnaire, physical inability to perform a 6-min walking test or serious disease at the time of inclusion. After written informed consent was obtained, patients were asked to complete a selfadministered questionnaire and to perform a 6-min walking test, which is preferable to other exercise testing because of its better acceptance and feasibility [32]. The consulting cardiologist registered the functional status according to the NYHA classification and scheduled an appointment for echocardiography if this had not been performed during the previous 6 months. Patients who agreed to participate were asked to fill out the questionnaire at home for a second time after a period of 2 weeks and to mail it back in a prepaid envelope. If questionnaires were incomplete, patients were contacted by telephone for additional answers. 2.3. Scoring Each item on the questionnaire was to be answered in Likert format of five categories. Patients were instructed to answer all questions by putting a sign in front of the most appropriate answer. The written introduction to the questionnaire made it clear that there were no right or wrong answers and that all items needed to be completed. The score was reversed on certain items so that a high score consistently represented a better QoL. Sumscores were calculated for all scales identified with factor analysis and transformed, to obtain values ranging from 0 to 100 with 100 representing perfect QoL. This might not be the best way to reflect QoL; however, it is in agreement with the methods used in scoring the SF-36, and therefore the easiest to interpret by the reader. 2.4. Analysis The responses to the questionnaire were subjected to recommended tests of reliability and validity [1,33,34]. Psychometric properties of the Aquarel questionnaire were analysed in six ways: (1) The individual items were subjected to factorial analysis using varimax rotation in the SPSS (Statistical Package for the Social Sciences) Factor Analysis program, to simplify the overall structure [35]; (2)
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internal consistency of the obtained scales was evaluated using Cronbach’s alpha; (3) confirmation of the scale structure was assessed by obtaining correlations between scales using Pearson correlation coefficient; (4) content validity was analysed through the correlations of the specific scales to the SF-36, NYHA classification, echocardiographic findings and results of the 6-min walking test; (5) test–retest reliability was evaluated by intraclass correlations (ICC) calculated on data produced from one-way analysis of variance [36] and (6) by the Bland and Altman method on Aquarel items selected for the preliminary version of the questionnaire [37]. ICC analyses were specifically designed to examine reliability, providing a reliability index to indicate the measurement error. Bland and Altman’s method assesses agreement between clinical measurements, based on analysis of differences between measurements. This combination of tests was done because neither test alone provides sufficient information. 3. Results 3.1. Patient characteristics Seventy-four patients were included. Table 1 summarizes the demographic and clinical characteristics together with the response rates. The overall proportion of returned second questionnaires was high for a postal survey (98.7%) [38,39]. The distribution of age, sex, NYHA classification and pacing modes is representative for patient populations at outpatient clinics in the Netherlands [40]. 3.2. Factor analysis A first factor analysis extracted seven factors or subgroups of items containing interrelated information on the Aquarel questionnaire, based on eigenvalues larger than 1.0, which is the criterion used by rule [34]. The fifth subgroup clearly represented cognitive functioning (items 18–21, see the Appendix), but no clear subscales on disease-specific complaints could be identified. When the items on cognition were left out and a second factor analysis was done, three additional subscales could be composed (Table 2). Responses to questions 7–10 (dyspnea on exertion) and 22–24 (fatigue) were highly interrelated, and could be labelled as a physical dimension. Questions 1–6 (chest pain) and 11–12 (dyspnea at rest) formed a second subgroup that was labelled as chest discomfort. The third subgroup contained interrelated items 13–17 and was labelled as arrhythmias. With the second factor analysis three problematic items (25–27) were identified and therefore discarded from the final version of the questionnaire. 3.3. Distribution of scores and internal consistency of scales Both are presented in Table 3. The mean scores on each scale were between 60 and 90, indicating a moderate impact of pacemaker therapy on QoL. The mean scores did not dif-
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Table 1 Sociodemographic and clinical characteristics of the patients (n⫽74) Response rate (%) Age (mean ⫾ S.D.) Sex (number and % of men) Marital status (%) Married or cohabiting Single Divorced Widow Level of education (%) Primary education Secondary education University education Occupation (%) Retired Full time job Housewife Disability Unemployed Cardiovascular medication (%) Antiarrhythmic drugs ACE inhibitors Digoxin Pacing mode (%) DDDR DDD VVIR VVI AAIR AAI Years since first implant (mean ⫾ S.D.) NYHA classification (%) Class I Class II Class III Class IV Indication for PM implantation (%) Atrioventricular block Sinus node disease Bradytachy syndrome Atrial fibrillation with slow ventricular rate
98.7 65.9 ⫾ 13 47 (63.5) 82.4 5.4 2.7 9.5 29.7 51.4 19.0 45.9 12.2 17.6 21.6 1.4 35.1 41.9 16.2 23.0 10.8 43.2 14.9 1.4 2.7 8.6 ⫾ 6.2 32.4 48.6 18.9 — 70 15.7 8.6 5.7
fer too much from the median values and visual inspection of the distribution of scores revealed a quite normal distribution. Internal consistency was assessed with Cronbach’s alpha coefficient. It has been suggested that a coefficient of ⬎0.5 is acceptable, although ideally scores should be ⭓0.7 [41]. All of the identified subscales met the last criterium. Since alpha values are generally lower for domains containing very few statements these results are indeed satisfying. 3.4. Content validity For measurements of QoL gold standards do not exist and therefore validity testing is challenging. Construct validation begins with a conceptual definition of the topic to be measured, indicating the theoretical relationship of scale scores to external criteria, such as other health measurement scales or other methods that measure the same concept [1]. An example is the correlation of 6-min walking distance with the score on the dimension physical functioning. The hypothesis put forward was that patients with short 6-min
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Table 2 Disease-specific dimensions of the Aquarel questionnaire based on a second factor analysis Factor 1 Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Item 7 Item 8 Item 9 Item 10 Item 11 Item 12 Item 13 Item 14 Item 15 Item 16 Item 17 Item 22 Item 23 Item 24 Item 25 Item 26 Item 27
Factor 2
.303
Factor 3
.609 .838 .721 .669 .826 .761
.838 .828 .803 .809 .369 .304 .335
.304
.591 .572
.341 .600 .687 .631 .626 .628
.314
.541 .640 .693 .354 .493
⫺.331 .423
.468 .303
Values lower then .3 are suppressed.
walking distance, a lower NYHA classification or ventricular pacing would have a lower QoL score, and that left ventricular end diastolic diameter would not correlate with QoL scores. Furthermore, a small to moderate correlation was expected with the SF-36. The correlation between comparable dimensions should be higher than the correlations between less comparable dimensions. The expected relations were generally observed (Table 4). Moderate correlations between the dimensions of the Aquarel and the SF-36 were found. Comparison of mean scores between patients according to pacing mode, 6-min walk distance and NYHA classification revealed significant differences as demonstrated in Table 5. There was a negative correlation of the QoL scores with NYHA classification (higher classification related to worse QoL) and a positive correlation with the results of 6-min walking test. Furthermore, QoL scores were in favour
of dual chamber pacing. These findings are an indication for construct validity. 3.5. Test–retest reliability In trials, QoL scores must have a high reliability when a condition is stable in order to be confident that changes in scores are related to treatment. Test–retest reliability calculations revealed that the Aquarel QoL questionnaire was stable upon repeated administration from baseline to 1–2 weeks. The correlation coefficients between first and second measurement varied from 0.79 to 0.92, indicating a good degree of association between the test and retest scores. ICCs were moderate to excellent for all scales (0.80 to 0.91), thereby exceeding 0.70 as the acceptable value for group comparisons in clinical studies [34]. However, these values do not indicate the direction of the association and therefore repeatability was also assessed by the method recommended by Bland and Altman [37]. The differences between two measurements (with a 1–2week interval) were plotted against the overall mean of the two measurements. The variance of the differences was calculated and 95% confidence intervals (CI) constructed. Patients with the same values for average and difference in scores were represented by SPSS as one dot. All dots outside the 95% CI were therefore checked and appeared to represent a single case. So there appeared to be no relation between the difference and the mean (Fig. 1), demonstrating a constant level of error, independent of the value of the mean. The dots outside the 95% CIs are not on one side, indicating that scores on the second questionnaire were not systematically higher or lower with repeated administration. The mean of the differences was not statistically significantly different from zero, indicating that there is no systematic error.
4. Discussion Over the past decades there has been a rapid development of highly sophisticated pacing devices and an increasing
Table 3 Score distribution and scales reliability
Questionnaire 1 Cognitive functioning Chest discomfort Dyspnea on exertion Arrhythmias Questionnaire 2 Cognitive functioning Chest discomfort Dyspnea on exertion Arrhythmias
n
Means of scores
Medians of scores
S.D.
Cronbach’s ␣
74 74 74 74
69.00 85.29 64.03 80.95
68.75 90.63 60.71 85.00
19.86 15.48 20.38 16.40
.75 .89 .90 .73
73 73 73 73
68.15 86.14 65.24 79.79
68.75 90.63 61.29 80.00
21.22 13.15 21.21 17.25
.81 .83 .92 .74
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Table 4 Multidimensional matrix of Pearson correlation coefficients for Aquarel and SF-36 Aquarel
Aquarel: Cognition Chest discomfort Dyspnea & exertion Arrhythmias SF-36: Physical functioning Social functioning Role functioning (phys.) Role functioning (emo.) Mental health Vitality Pain General health
Cognition
Chest discomfort
Dyspnea & exertion
.43 .53 .46
.54 .47
.45
.42 .58 .31 .27 .49 .39 .36 .49
.47 .41 .36 .37 .48 .40 .63 .61
.83 .52 .69 .46 .46 .69 .60 .78
Arrhythmias
.36 .42 .31 .23 .46 .38 .38 .46
naires and the conflicting results [7,14], the value of the QoL results obtained can be questioned. To prevent noncomparable pacing reports it is desirable to have a standard questionnaire for evaluation of QoL. The purpose of this study was to assess the characteristics and feasibility of a new self-administered QoL questionnaire, designed for pacemaker patients specifically “Aquarel.” The psychometric properties (validity and reliability) of this questionnaire were found satisfactory and suggest this instrument to be valid and reliable. The inter scale correlations within the Aquarel questionnaire as well as with the SF-36 were moderate, demonstrating their individual value and distinctiveness. As hypothesised, the highest correlations with the SF-36 were found between comparable dimensions. Two subscales (cognition and arrhythmias) of the Aquarel appeared to perform quite poorly (Table 5). This
number of indications for implant [42]. Since age at first implant is about 75 years and exercise capacity generally low, the question remains whether implantation of expensive pacemakers and the associated escalating costs are justified. Therefore, the evaluation of proper pacemaker therapy should not merely be based on clinical outcomes like maximal exercise capacity, but on an assessment of QoL as well. Stofmeel et al. [20] performed a review of the literature on this topic. Fourteen studies using multi-item questionnaires for evaluating QoL in DDD pacing compared to VVI(R) pacing were selected for review. Most of the studies showed improved QoL of dual-chamber pacing compared to ventricular pacing (with, as well as without, rate adaptation). Differences in QoL scores were nonsignificant in several studies and most other studies did not show consistent QoL effects in all scales used. In view of the fact that only two studies used validated (nondisease-specific) question-
Table 5 Mean scores according to pacing mode, 6-min walk test and NYHA classification Pacing mode
SF-36 Physical functioning Social functioning Role functioning (phys.) Role functioning (emo.) Mental health Vitality Pain General health Aquarel Cognition Chest discomfort Dyspnea & exertion Arrhythmias
6-min-walktest
NYHA
Atrial/dual (n⫽43)
Ventricular (n⫽28)
⬍375 mtr (n⫽27)
⭓375 mtr (n⫽47)
I (n⫽24)
II (n⫽36)
III (n⫽14)
73.13 87.95 61.61 71.43 76.71 70.77 86.88 66.81
54.02* 75.00* 45.35 68.99 69.42 57.44* 73.37* 51.79*
40.00 72.22 25.93 49.38 67.56 51.67 64.17 44.76
72.78* 82.45 67.02* 80.14* 74.23 68.87* 87.45* 65.22*
82.94 89.06 81.25 86.11 80.71 77.78 90.05 74.57
55.56 75.69 41.67 62.04 64.00 55.97 77.10 53.68
36.43* 68.75* 28.75* 57.14* 76.57* 53.57* 64.72* 40.71*
74.55 90.29 73.72 84.11
65.99 82.02* 57.70* 78.14
67.36 78.54 50.55 76.30
69.95 89.16* 71.78* 83.62
73.44 92.19 80.36 86.25
69.10 82.99 59.78 77.78
61.16 79.37* 46.98* 80.00
* P value of independent T test or one-way-ANOVA ⬍0.05.
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Fig. 1. Difference against average scores on Aquarel subscales.
result can be explained by the fact that the studied group of patients had a pacemaker implanted since 8.6 (mean) years. The added value of these two subscales of the Aquarel is likely to be put forward when looking at patients before and after primo implantation of a pacemaker. Therefore, these scales are not omitted from the Aquarel questionnaire for the time being. This study has a number of limitations. First, only 74 subjects were studied. This number of subjects was sufficient to demonstrate psychometric properties, but a larger group of patients would test its performance more firmly, especially the factor analysis. Secondly, repeatability was very acceptable on group level as demonstrated with different techniques, but it should be recognised that the difference between test and retest without a significant change in health can rise up to about 20 points (Fig. 1), which limits the usefulness of this instrument for evaluation of QoL in individual patients. To determine which change in score represents an important change in health, a larger number of patients needs to be evaluated in a longitudinal designed
study. Thirdly, sex and age were unequally distributed among the subgroups within pacing mode, 6-min walk test and NYHA. However, multivariate analyses including sex and age did not materially affect the results (data not shown). Finally, the Aquarel QoL questionnaire was tested in one institution only. 5. Conclusion This study has demonstrated the feasibility and usefulness of a self-administered QoL questionnaire for pacemaker patients, when added to the SF-36. Depending on the results of ongoing research into its responsiveness to change, and whether it is judged that the cost of collecting this information is justified, the Aquarel questionnaire may well prove to be an outcome measure suitable for use in studies with pacemaker patients. Results obtained in this validation study are promising and we anticipate to corroborate these results in further studies using the Aquarel questionnaire.
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Appendix. Preliminary version of Aquarel 1. Have you felt discomfort in the chest? ⵧ no discomfort at all ⵧ very mild discomfort ⵧ mild discomfort ⵧ moderate discomfort ⵧ great discomfort 2. Do you get chest discomfort while walking upstairs or uphill? ⵧ no discomfort ⵧ very mild discomfort ⵧ mild discomfort ⵧ moderate discomfort ⵧ severe discomfort 3. Do you get chest discomfort while walking quickly on level ground? ⵧ no discomfort ⵧ very mild discomfort ⵧ mild discomfort ⵧ moderate discomfort ⵧ severe discomfort 4. Do you get chest discomfort while walking on level ground at the same pace as people usually do at your age? ⵧ no discomfort ⵧ very mild discomfort ⵧ mild discomfort ⵧ moderate discomfort ⵧ severe discomfort 5. Have you been restricted by chest discomfort during physical exercise? ⵧ not restricted at all ⵧ slightly restricted ⵧ moderately restricted ⵧ very restricted ⵧ extremely restricted 6. Have you experienced chest discomfort at rest? ⵧ no discomfort ⵧ very mild discomfort ⵧ mild discomfort ⵧ moderate discomfort ⵧ severe discomfort 7. Do you get short of breath while walking upstairs or uphill? ⵧ not short of breath ⵧ very mildly short of breath ⵧ mild short of breath ⵧ moderate short of breath ⵧ extreme short of breath 8. Do you get short of breath while walking quickly on level ground? ⵧ not short of breath ⵧ very mildly short of breath ⵧ mild short of breath ⵧ moderate short of breath
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ⵧ extreme short of breath 9. Do you get short of breath while walking on level ground at the same pace as people usually do at your age? ⵧ not short of breath ⵧ very mildly short of breath ⵧ mild short of breath ⵧ moderate short of breath ⵧ extreme short of breath 10. Have you been restricted by breathlessness during physical exercise? ⵧ not restricted at all ⵧ slightly restricted ⵧ moderately restricted ⵧ very restricted ⵧ extremely restricted 11. Have you been out of breath at rest? ⵧ not out of breath ⵧ slightly out of breath ⵧ moderately out of breath ⵧ very out of breath ⵧ extremely out of breath 12. Do you awake when sleeping due to shortness of breath? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 13. Did you have swollen ankles? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 14. Have you suffered from an irregular heartbeat? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 15. Have you suffered from heart pounding? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 16. Have you suffered from pounding in the neck or abdomen? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 17. Have you felt close to fainting?
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ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 18. Have you had trouble in making up your mind? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 19. Have you had trouble with remembering things? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 20. Have you had difficulty in concentration? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 21. Have you had trouble falling asleep? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously 22. Do you feel tired and exhausted after a night’s sleep? ⵧ never ⵧ seldom ⵧ once in a while ⵧ often ⵧ continuously 23. Have you been restricted in your daily activities due to tiredness or lack of energy? ⵧ extremely restricted ⵧ very restricted ⵧ moderately restricted ⵧ slightly restricted ⵧ not restricted at all 24. Do you have to sit or lie down during the day to rest? ⵧ never ⵧ seldom ⵧ once in awhile ⵧ often ⵧ continuously
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