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Validation of the short-form Health Literacy Scale in patients with stroke
Patient Education and Counseling 98 (2015) 762–770
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Assessment
Validation of the short-form Health Literacy Scale in patients with stroke Yi-Jing Huang a,1, Yu-Lin Wang b,c,1, Tzu-Yi Wu a, Cheng-Te Chen d, Ken N. Kuo e, Sheng-Shiung Chen f, Wen-Hsuan Hou g,h,i,1,*, Ching-Lin Hsieh a,j,1 a
School of Occupational Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan Rehabilitation Department, Chi Mei Medical Center, Tainan, Taiwan Department of Sports Management, Chia Nan University of Pharmacy and Science, Tainan, Taiwan d Center for Teacher Education, National Tsing Hua University, Hsinchu, Taiwan e Center for Evidence-Based Medicine, Taipei Medical University, Taipei, Taiwan f Department of Physical Medicine and Rehabilitation, E-Da Hospital/I-Shou University, Kaohsiung, Taiwan g Master Program in Long-Term Care, College of Nursing, Taipei Medical University, Taipei, Taiwan h School of Gerontology and Health Management, College of Nursing, Taipei Medical University, Taipei, Taiwan i Department of Physical Medicine and Rehabilitation, Taipei Medical University Hospital, Taipei, Taiwan j Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan b c
A R T I C L E I N F O
A B S T R A C T
Article history: Received 14 July 2014 Received in revised form 12 November 2014 Accepted 20 February 2015
Objective: We aimed to validate a Mandarin version of the short-form Health Literacy Scale (SHEAL) in patients with stroke. Methods: Each patient with stroke was interviewed with the SHEAL. The Public Stroke Knowledge Quiz (PSKQ) was administered as a criterion for examining the convergent validity of the SHEAL. The discriminative validity of the SHEAL was determined with age and education level as independent grouping variables. Results: A total of 87 patients with stroke volunteered to participate in this prospective study. The SHEAL demonstrated sufficient internal consistency reliability (alpha = 0.82) and high correlation with the PSKQ (r = 0.62). The SHEAL scores between different age groups and education level groups were significantly different. The SHEAL, however, showed a notable ceiling effect (24.1% of the participants), indicating that the SHEAL cannot differentiate level of health literacy between individuals with high health literacy. Conclusion: The internal consistency reliability, convergent validity, and discriminative validity of the SHEAL were adequate. However, the internal consistency reliability and ceiling effect of the SHEAL need to be improved. Practice implications: The SHEAL has shown its potential for assessing the health literacy of patients with stroke for research purposes. For clinical usage, however, the SHEAL should be used with caution. ß 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Health literacy Psychometrics Validation Measurement Stroke
1. Introduction Stroke is a chronic disease and has become the leading cause of death and serious, long-term disability globally [1]. More than 7.1% of the world population are affected by stroke annually [1]. To manage chronic diseases and long-term disabilities requires the
* Corresponding author at: Master Program in Long-Term Care, College of Nursing, Taipei Medical University, No. 250, Wuxing St., Xinyi Dist., Taipei City 110, Taiwan. Tel.: +886 2 2736 1661x6311. E-mail address: [email protected] (W.-H. Hou). 1 These authors contributed equally to this paper. http://dx.doi.org/10.1016/j.pec.2015.02.021 0738-3991/ß 2015 Elsevier Ireland Ltd. All rights reserved.
active participation of the patients [2–5], and this can only occur when patients have adequate health literacy [6–9]. Health literacy is defined as the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions [10]. Health literacy is an essential aspect of self-management and shared decision-making to improve health outcomes in patients with stroke. Numerous studies have highlighted the importance of an adequate level of health literacy to the disease management process [11–14] and noted that inadequate health literacy is a potentially modifiable determinant of poor health outcomes in people with chronic disease [15–18]. Thus, it is important to assess
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the health literacy of stroke survivors early on in order to identify patients at risk of low literacy. Such information is useful for clinicians to ameliorate patients’ health literacy and help them manage their health. Measures of health literacy with sound psychometric properties are a prerequisite to successfully understanding, monitoring, and managing patients’ health literacy. To date, more than a dozen validated measures of health literacy have been developed [19– 21]. Although these measures have been used in several adult or patient populations, their usefulness and applicability for patients with stroke remain unknown. To the best of our knowledge, no measures assessing health literacy have been validated in patients with stroke, which not only hampers clinicians in assessing and understanding the health literacy required for stroke management, but also hinders researchers investigating the concepts of strokespecific health literacy skills. Thus, there is a need to validate existing health literacy measures in patients with stroke, in order to provide clinicians and researchers empirical evidence for assessing and managing health literacy in stroke populations. The short-form Health Literacy Scale (SHEAL) was designed to assess the general population’s comprehension and numeracy skills needed to promote health, seek health care, and manage selfcare [22]. The SHEAL contains 11 items simplified from the Health Literacy Scale [22,23]. The SHEAL is brief and quick to administer (around 5 min), so it could be an efficient measure for assessing health literacy in busy clinical settings [22]. The SHEAL also shows satisfactory psychometric properties (including internal consistency reliability, factorial validity, convergent validity and discriminative validity) in the general public [22]. Hence, the SHEAL is a potential measure for assessing health literacy in patients with stroke. However, the SHEAL has not been validated in patients with stroke. The psychometric properties of a measure are sample dependent [24,25], and all relevant psychometric properties must be examined comprehensively in patient samples to ensure quality of assessment [24]. Consequently, despite the fact that the SHEAL has been validated in the general population, the psychometric findings from the previous study cannot be directly applied to patients with stroke. The psychometric properties of the SHEAL have to be validated in patients with stroke to provide empirical evidence to support its use in these patients. The purpose of this study was to examine the psychometric properties (including internal consistency reliability, convergent validity, and discriminative validity) of the SHEAL in patients with stroke. We hypothesized that the SHEAL would have good internal consistency reliability, as well as sufficient convergent validity and good discriminative validity. 2. Methods
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patient. We excluded patients with aphasia or severe cognitive impairments (Mini-Mental State examination score <22 [27]) who had difficulty completing the interview and providing reliable responses. This study received approval from the ethical review committees of the two hospitals. 2.2. Procedures We used convenience sampling to recruit subjects who were accessible and eligible. After being referred to the interviewer by therapists, potential and accessible subjects were invited to participate in this study. Subjects who agreed to participate in this study received screening tests to determine eligibility. Eligible subjects were interviewed face-to-face by an experienced research assistant with a Mandarin version of the SHEAL and a Mandarin version of the Public Stroke Knowledge Quiz (PSKQ). A set of questions regarding demographic data and stroke related information was completed by participants or obtained from their medical charts. During the interview, the patient’s family members could stay by the patient’s side but could not actively influence the patient. 2.3. Measure The Mandarin version of the SHEAL assesses adults’ health literacy in terms of their ability to read, comprehend, and utilize basic health information in making personal health decisions [22]. The SHEAL was simplified from the Health Literacy Scale, which was developed based on the definition of health literacy proposed by the Institute of Medicine (2004) and the National Research Council (2005), and comprises questions regarding prose, document, and numeracy skills [10,23,28]. The SHEAL contains 11 multiple-choice items, of which 8 test comprehension (prose and document) abilities and 3 assess numeracy skills. Each correct response receives 1 point; incorrect responses receive 0 points. The total score ranges from 0 to 11. Higher scores indicate better health literacy. The Mandarin version of the PSKQ [29] was designed by the Taiwan Stroke Association to assess knowledge of stroke among the general public. We chose the PSKQ as the criterion to estimate the convergent validity of the SHEAL. The selection was based on previous studies that showed a significant correlation between health literacy and health knowledge [12,30,31]. The quiz comprises 10 true/false items and 10 multiple-choice items that evaluate basic stroke-related knowledge, including prevention, warning signs, symptoms, emergency response, treatment, and prognosis of stroke. An incorrect answer for each item is scored as 0 and a correct answer is scored as 1. The total score ranges from 0 to 20. Higher scores indicate higher levels of stroke knowledge.
2.1. Participants 2.4. Statistical analysis This study was conducted between July 1 2013, and October 31 2013. Although there are no commonly accepted methods for calculating the required sample size in a psychometric study, a sample size of at least 50–100 subjects is generally recommended [26]. Subjects were recruited from the rehabilitation departments of two teaching hospitals in northern Taiwan. Patients were invited to participate in the study if they met the following criteria: (1) diagnosis (International Classification of Diseases, Ninth Revision, Clinical Modification codes) of cerebral hemorrhage (431), cerebral infarction (434), or others (430, 432, 433, 436, 437) with stroke symptoms (e.g., hemiparesis or hemiplegia) confirmed by a neurologist, (2) age 20 years, (3) ability to complete the interview and to provide reliable outcomes as judged by the interviewer, and (4) written informed consent for participation obtained from the
We analyzed the distribution of the demographic characteristics of participants, the distribution of the SHEAL scores, and the internal consistency reliability and validity (convergent validity and discriminative validity) of the SHEAL. The floor and ceiling effects, the percentages of the sample scoring the minimum and maximum possible scores, respectively, reflect the extent to which scores cluster at the bottom and top of the scale range. Floor and ceiling effects >15% were considered to be significant [32]. The internal consistency reliability of the SHEAL was determined by Cronbach’s alpha. An alpha coefficient greater than 0.70 was considered adequate for group comparison (e.g., using the SHEAL scores for a group of participants, commonly for research
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purposes), while a coefficient greater than 0.90 was considered adequate for individual comparison (e.g., using the SHEAL score for a patient in a clinical setting) [33]. We also conducted item analysis by examining the mean inter-item correlation and corrected itemtotal correlation of each item in the SHEAL. It is recommended that the mean inter-item correlation exceed 0.30 [34], and that the corrected item-total correlation exceed 0.40 [35]. To estimate the convergent validity of the SHEAL, we examined the strength of the correlation between the SHEAL scores and the scores of the PSKQ using the Pearson correlation coefficient. An r coefficient >0.60 indicates high convergent validity; 0.30–0.60, moderate; and <0.30, poor [36]. To examine the discriminative validity of the SHEAL, we selected two variables—age and education level—because of previous evidence showing that health literacy was significantly related to age and educational attainment [18,31,37,38]. The ability of the SHEAL to discriminate between groups of participants was investigated by comparing mean scores between middle-aged and elderly participants (<60 and 60 years old) and between 2 education level groups (<10 and 10 years of formal education) using two-way analysis of variance (ANOVA). All statistical analyses were conducted using SPSS 15.0 Software (SPSS Inc., Chicago, IL, USA). Two-sided p < 0.05 was considered statistically significant. 3. Results 3.1. Demographics of the participants A total of 87 (54% male) patients with stroke joined this study. The average age of the participants was 57 years. The majority of
Gender Male Female Age Years of formal educationa 1–6 7–12 13–16 17 Occupation Retired Unemployed Labor Manager Urbanization level of residencea Moderately to highly urbanized cities Developing cities Rural areas Sources of patients Outpatients Inpatients Types of stroke Hemorrhagic Ischemic Others Months after strokea <6 months (subacute stage) 6 months (chronic stage) Affected side Left Right Both Modified Rankin Scale Public Stroke Knowledge Quiz Short-form Health Literacy Scale a
Mean (SD)
n (%) 47 (54.0%) 40 (46.0%)
57.4 (15.1) 20 12 30 3
(23.0%) (13.8%) (34.5%) (3.4%)
37 32 15 3
(42.5%) (36.8%) (17.2%) (3.4%)
64 (73.6%) 12 (13.8%) 7 (8.0%) 77 (88.5%) 10 (11.5%) 31 (35.6%) 52 (59.8%) 4 (4.6%) 21.3 (25.8) 24 (27.6%) 55 (63.2%) 54 (62.1%) 29 (33.3%) 4 (4.6%) 2.5 (1.1) 13.3 (3.1) 8.1 (2.8)
Total percentages do not add up to 100 due to missing values.
the participants were outpatients with chronic stroke (6 months post stroke) and diagnosed as ischemic stroke (63.2% and 59.8%, respectively). The average duration after stroke of the participants was 21 months. Most of the participants had 10–16 years of formal schooling (senior high to college) and lived in urbanized cities. Other demographic characteristics of the stroke patients are shown in Table 1. 3.2. Distribution of the SHEAL scores
Table 1 Demographic characteristics of the participants (n = 87). Variable
Fig. 1. Histogram with normal curve superimposed over the distribution of total scores of the short-form Health Literacy Scale.
The mean SHEAL score was 8.1 in the study sample. Fig. 1 shows the distribution of the SHEAL scores. In examining the floor and ceiling effects of the SHEAL, we found that 1% of the patients obtained the lowest score of the SHEAL and 24% of them obtained the highest score. Furthermore, regardless of time after stroke onset, more than 15% of the participants reached the highest score (20.8% and 23.6% for subacute stage and chronic stage, respectively). 3.3. Psychometric properties of the SHEAL With regard to the internal consistency reliability of the SHEAL, the alpha value was 0.82, which was higher than the criterion of 0.70 for group comparison but lower than that of 0.90 for individual comparison. Table 2 presents the results of item
Table 2 Results of item analysis of the SHEAL. Item number and item content
Mean inter-item correlation
Corrected item-total correlation
Cronbach’s alpha if item deleted
1. Symptom expression 2. Drug applications 3. Medical tests 4. Disease management 5. Patient name 6. Medication time 7. Medication frequency 8. Drug dosage 9. Prescription duration 10. Side effects 11. Precautions
0.25a 0.20a 0.12a 0.19a 0.37 0.33 0.29a 0.39 0.35 0.32 0.40
0.42 0.31b 0.18b 0.25b 0.62 0.58 0.46 0.67 0.61 0.54 0.70
0.82 0.82 0.83 0.82 0.80 0.80 0.81 0.79 0.80 0.80 0.79
a b
The mean inter-item correlation was below 0.30. The corrected item-total correlation was below 0.40.
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Fig. 2. Differences in the short-form Health Literacy Scale scores among different age and education level groups.
analysis. Among the 11 items in the SHEAL, items 2–4 showed both inadequate mean inter-item correlations and poor corrected itemtotal correlations. When these three less relevant items were removed from the SHEAL, Cronbach’s alpha increased from 0.82 to 0.85. Correlation between the scores of the SHEAL and that of the PSKQ was 0.62 (p < 0.001), indicating that the two scales were highly correlated. In terms of the discriminative validity (Fig. 2), a two-way ANOVA revealed significant age (F1, 80 = 7.79, p = 0.007) and education effects (F1, 80 = 5.49, p = 0.022) but no significant interaction between age and education (F1, 80 = 0.12, p = 0.73). 4. Discussion and conclusion 4.1. Discussion This study, to the authors’ knowledge, is the first to investigate the psychometric validity of the SHEAL in patients with stroke. Owing to the lack of health literacy measures validated in stroke survivors, no health literacy measures with robust psychometric evidence can be used in a stroke population. The findings of this study can provide psychometric evidence of the SHEAL for both clinicians and researchers to assess health literacy in patients with stroke. 4.1.1. Distribution of the SHEAL scores A floor/ceiling effect means a measure cannot differentiate between individuals with low/high levels of an underlying trait, respectively [32]. The SHEAL demonstrated no floor effect and a significant ceiling effect in patients with stroke. The results indicate that the SHEAL is able to discriminate the health literacy of individual patients with low health literacy but not able to distinguish that of individual patients with high health literacy. The ceiling effect of the SHEAL might be attributed to the fact that patients with stroke often have other chronic diseases (e.g., hypertension, diabetes mellitus) and have to receive long-term medication. These facts might have made the chronic patients more likely to be familiar with the items regarding physicianspatients dialogues in the outpatient clinics and prescription labels in the SHEAL. However, our results showed that regardless of time after stroke, the SHEAL had notable ceiling effects both in the participants with subacute stroke and in those with chronic stroke. Furthermore, a notable ceiling effect of the SHEAL (43.2% of a healthy adult sample received the highest score) was also found in a validation study [22]. These observations indicate that the items
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on the scale may be too easy for a high proportion (24.1%) of the participants with stroke, thus allowing their scores to cluster at the upper limit of the SHEAL. The SHEAL with a significant ceiling effect would have the following two flaws when it is administered in patients with higher level of health literacy. First, patients obtaining the highest possible score of the SHEAL does not necessarily imply a positive correlation with a high level health literacy - it may for example mean that the items in the SHEAL are not very challenging. Second, the ceiling effect limits the SHEAL’s ability to detect improvements in the health literacy of patients with scores clustered at the top of the scale [36,39]. In order to promote the utility of the SHEAL, it would be necessary to minimize the ceiling effect. Revising the scale by adding more challenging items (e.g., items assessing the abilities to calculate and comprehend graphs) may be warranted. However, it is noted that when the health information providers’ main concerns are patients with low health literacy, the ceiling effect of the SHEAL should be less problematic. 4.1.2. Internal consistency reliability Internal consistency reliability refers to the consistency among responses to the items within a measure [40]. Our results (alpha = 0.82) showed sufficient internal consistency reliability in the SHEAL, which means that the 11 items of the SHEAL are homogeneous in measuring stroke patients’ health literacy. In addition, the obtained alpha value might be an underestimate for the following two reasons: (1) the ceiling effect lowered the variability in the SHEAL scores, which would compromise the internal consistency reliability [41]; and (2) the 11 items of the SHEAL are dichotomous items, which tended to undervalue the strength of correlation and then decreased the alpha value [41]. Thus, the high level of internal consistency reliability (alpha = 0.82) reasonably suggests that the SHEAL is a reliable scale and is satisfactory for group comparison (i.e., research application). Through item analysis, however, we found that three items (items 2–4) had low correlations both with the other items and with the total scores of the SHEAL. These findings imply that the participants’ responses to the three items were less consistent as compared to those of the other items, and that they had lowered the alpha coefficient in this study [42]. Thus, to improve the internal consistency reliability of the SHEAL for individual comparisons (i.e., clinical application) in a stroke population, it would be necessary to drop the less relevant items and add more highly reliable items in the future. 4.1.3. Convergent validity Convergent validity represents the degree to which the construct of a measure assessing is correlated with the other construct(s) that are theoretically related [43]. The scores of the SHEAL were highly correlated with those of the PSKQ (Pearson’s r = 0.62). This result is consistent with previous studies demonstrating that health literacy is correlated with health knowledge [12,30,31]. In addition, because the ceiling effect of the SHEAL limited the variability in the scores, the correlation obtained is quite possibly an underestimate of the true magnitude of the correlation. Therefore, the high correlation supports the convergent construct validity of the SHEAL. 4.1.4. Discriminative validity Discriminative validity of a measure provides information on how well a measure differentiates, as expected, between participant groups who differ in their underlying trait [44,45]. Our results showed that given the same education level group, the SHEAL scores of the older participants were significantly lower than those of the younger participants; on the other hand, given the same age group, the SHEAL scores of participants with lower education levels were significantly lower than those of participants with
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higher education levels. These findings indicate that the SHEAL was able to uncover differences in health literacy between disparate age and educational attainment groups of patients with stroke. These results suggest that the SHEAL, having good discriminative validity, is useful for comparing patients’ health literacy levels in cross-sectional studies [46]. It can also assist clinicians in distinguishing between groups of patients with higher and lower health literacy, which may be useful for clinicians to identify patients needing early health literacy intervention [44]. 4.1.5. The SHEAL scores of the stroke patients The mean SHEAL score (8.1) in the study sample was somewhat lower than that of healthy adults in a previous survey (9.0) [22]. Our results demonstrated that the psychometric properties of the SHEAL are sound in patients with stroke. Such results may give us support to explain that the relatively low scores on the SHEAL represent the relatively low level of health literacy in the stroke patients as compared with that of healthy adults. Similar findings were reported in a previous study, which demonstrated that the average level of health literacy of patients following stroke was lower than that of their caregivers (indicative of healthy adults) [47]. These findings imply that stroke patients are more likely to have difficulty in dealing with health-related activities, such as communicating with clinicians and understanding prescriptions or instructions. 4.1.6. Limitations Four sampling issues may have threatened the external validity of this study. First, our participants were a convenience sample. Second, most of the participants were outpatients with chronic stroke and lived in moderately to highly urbanized cities, which might have caused a sampling bias in terms of time after stroke and place of residence. Third, our eligibility criteria excluded people who could not follow instructions to complete the assessment. Last, the size of the sample in our study was not large. Thus, the results should be cautiously generalized to patients at acute and subacute stages, as well as stroke patients with severe cognitive impairment or aphasia. Furthermore, the psychometric properties of the PSKQ are largely unknown, which might have threatened the internal validity of the findings. In addition, although this study provides preliminary support for the use of the SHEAL in patients with stroke, we did not examine the test-retest reliability, concurrent validity, factorial validity or responsiveness of the SHEAL. Further examination of the aforementioned properties is
needed to fully demonstrate the psychometric properties and utility of the SHEAL in patients with stroke. 4.2. Conclusions Our results support the internal consistency reliability, convergent validity and discriminative validity of the SHEAL in measuring health literacy in patients with stroke. However, we found that the SHEAL had a limited ability to distinguish between individuals with high levels of health literacy among stroke patients. To promote the utility of the SHEAL, it will be necessary to minimize the ceiling effect and to increase the internal consistency reliability of the scale. Further revision of the SHEAL is warranted; more challenging items should be added and less relevant items should be deleted. 4.3. Practice implications For future investigation of health literacy for patients with stroke, the SHEAL appears to be a valid and reliable measure. Our results lend support for the usage and further investigation of health literacy in patients with stroke. However, clinicians should apply the SHEAL with caution because the SHEAL might not be very precise for measuring health literacy in individual stroke patients, and the SHEAL might be too easy for some patients with high levels of health literacy. Conflicts of interest The authors have no conflicts of interest relevant to this article. Informed consent and patient details I confirm all patient/personal identifiers have been removed or disguised so the patient/person(s) described are not identifiable and cannot be identified through the details of the story. Acknowledgements This study was supported by research grants from the Taipei Medical University (TMU101-AE1-B21), Chi Mei Medical Center (103CM-TMU-12), E-Da Hospital (EDAHT103019), Ministry of Science and Technology (102-2314-B-038-007-MY3) and National Health Research Institutes (NHRI-EX102-10207PI).
Appendix: The short-form Health Literacy Scale
Part 1: Physician-patient Dialogues in outpatient clinics The following items are simulated conversations with your doctor at the clinic. Please choose the most appropriate answer from the options according to the description of each item. (
) 1.
Doctor, my right big toe has been painful for 4-5 days. It gets more and more painful and _____. The pain hasn’t been relieved at all. (1) obese (2) swollen (3) dehydrated
Y.-J. Huang et al. / Patient Education and Counseling 98 (2015) 762–770
( ) 2.
Paronychia is a kind of tissue inflammation. I’ll prescribe some _____ for you in order to relieve the pain and swelling. (1) antibiotics (2) antihypertensive drugs (3) hormones
(
) 3.
Have you had diabetes? At the next visit, please _____ and take this blood examination sheet to do a blood test at the department of laboratory medicine. (1) hold your urine (2) fast (3) eat
( ) 4.
After returning home, don’t wear shoes that are _____ temporarily. Keep your foot dry and breathable. If it doesn’t worsen, consult outpatient follow up after 5 days. (1) too tight (2) too soft (3) too loose
Part 2: Prescription Labels Date Dispensed Oct. 10, 2007
Prescription No.
N-0034
Patient Name
Da-Tong Li
History No.
25688652
Birthday
May 28, 1967
Gender
Male
Administration
Oral once a day 30 minutes before breakfast
Dosage
1/2 tablet each time
Drug Name
Euglucon 5 mg / tablet
Duration
14 days
Composition
Glyburide
Quantity
7 tablets
Appearance
tablet
Clinical Uses
Increase insulin secretion to lower blood sugar
Side effects
May cause low blood sugar (cold sweats, palpitations, headaches,
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shakiness, dizziness), fever, sore throat, skin rash, jaundice, etc. Precautions
Avoid driving or operating heavy machinery until your blood sugar level is stable. Do not drink alcohol while taking this drug. Please take sunburn protection measures.
Physician
Yi-Lin Wang
Dispensing Pharmacist
Zhong-Xin Lin
Verifying Pharmacist
Da-Ming Li
Please answer the following questions and choose the most appropriate option according to the contents of the prescription: (
) 5.
What is the name of the patient who takes this drug? (1) Yi-Lin Wang (2) Da-Tong Li (3) Zhong-Xin Lin
(
) 6.
When should the patient take this drug? (1) 30 minutes before meals (2) 30 minutes before sleep (3) 30 minutes after meals
(
) 7.
If the patient took this drug before breakfast today, it is better to take the next dose _____. (1) before dinner today
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(2) before breakfast tomorrow (3) before lunch tomorrow (
) 8.
How many drugs should the patient take each time? (1) 1/2 tablet (2) 1 tablet (3) 5 tablets
(
) 9.
The physician prescribed a total course of _____ days. (1) 1 (2) 7 (3) 14
(
) 10.
Taking this drug may cause side effects associated with low blood sugar, such as symptoms of _____. (1) skin rash (2) jaundice (3) palpitations
(
) 11.
Patients taking this drug should avoid driving or operating heavy machinery until their _____ level is stable. (1) blood pressure (2) blood sugar
(3) urinary protein
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[18] Schillinger D., Grumbach K., Piette J., Wang F., Osmond D., Daher C., et al. Association of health literacy with diabetes outcomes. J Am Med Assoc 2002;288:475–82. [19] Mancuso J.M.. Assessment and measurement of health literacy: an integrative review of the literature. Nurs Health Sci 2009;11:77–89. [20] Jordan J.E., Osborne R.H., Buchbinder R.. Critical appraisal of health literacy indices revealed variable underlying constructs, narrow content and psychometric weaknesses. J Clin Epidemiol 2011;64:366–79. [21] Al Sayah F., Williams B., Johnson J.A.. Measuring health literacy in individuals with diabetes: a systematic review and evaluation of available measures. Health Educ Behav 2013;40:42–55. [22] Lee S.Y., Tsai T.I., Tsai Y.W., Kuo K.N.. Development and validation of the short-form Mandarin Health Literacy Scale. Taiwan J Public Health 2012;31:184–94. [23] Tsai T.I., Lee S.Y., Tsai Y.W., Kuo K.N.. Methodology and validation of health literacy scale development in Taiwan. J Health Commun 2011;16:50–61. [24] Hobart J., Freeman J., Thompson A.. Kurtzke scales revisited: the application of psychometric methods to clinical intuition. Brain 2000;123:1027–40. [25] Cronbach L.J.. Essentials of psychological testing. New York: Harper and Row; 1949. [26] Institute for Health and Care Research. Questionnaires: selecting, translating and validating; 2010, Available at: http://www.emgo.nl/kc/preparation/ research%20design/ 8%20Questionnaires%20selecting,%20translating%20and%20validating.pdf [accessed 24.09.14]. [27] Folstein M.F., Folstein S.E., McHugh P.R.. Mini-mental state. A practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 1975;12:189–98. [28] National Research Council: measuring literacy: performance levels for adults. Washington, DC: The National Academies Press; 2005. [29] Taiwan Stroke Association. Public Stroke Knowledge Quiz. Taiwan Stroke Association; 2007 , Available at: http://www.strokecare.org.tw/quiz.doc [accessed 15.08.13]. [30] Gazmararian J.A., Williams M.V., Peel J., Baker D.W.. Health literacy and knowledge of chronic disease. Patient Educ Couns 2003;51:267–75. [31] Kalichman S.C., Benotsch E., Suarez T., Catz S., Miller J., Rompa D.. Health literacy and health-related knowledge among persons living with HIV/AIDS. Am J Prev Med 2000;18:325–31. [32] Terwee C.B., Bot S.D., de Boer M.R., van der Windt D.A., Knol D.L., Dekker J., et al. Quality criteria were proposed for measurement properties of health status questionnaires. J Clin Epidemiol 2007;60:34–42.
[33] Aaronson N., Alonso J., Burnam A., Lohr K.N., Patrick D.L., Perrin E., et al. Assessing health status and quality-of-life instruments: attributes and review criteria. Qual Life Res 2002;11:193–205. [34] El Moussaoui R., Opmeer B.C., Bossuyt P.M.M., Speelman P., de Borgie C.A.J.M., Prins J.M.. Development and validation of a short questionnaire in community acquired pneumonia. Thorax 2004;59:591–5. [35] McHorney C.A., Ware Jr JE, Lu J.F., Sherbourne C.D.. The MOS 36-item ShortForm Health Survey (SF-36): III. Tests of data quality, scaling assumptions, and reliability across diverse patient groups. Med Care 1994;32:40–66. [36] Andresen E.M.. Criteria for assessing the tools of disability outcomes research. Arch Phys Med Rehabil 2000;81(Suppl. 2):S15–20. [37] Beers B.B., McDonald V.J., Quistberg D.A., Ravenell K.L., Asch D.A., Shea J.A.. Disparities in health literacy between African American and non-African American primary care patients. J Gen Intern Med 2003;18:169. [38] Cho Y.I., Lee S.Y., Arozullah A.M., Crittenden K.S.. Effects of health literacy on health status and health service utilization amongst the elderly. Soc Sci Med 2008;66:1809–16. [39] Fitzpatrick R., Davey C., Buxton M.J., Jones D.R.. Evaluating patient-based outcome measures for use in clinical trials. Health Technol Assess 1998;2:i–v. 1–74. [40] Tavakol M., Dennick R.. Making sense of Cronbach’s alpha. Int J Med Educ 2011;2:53–5. [41] Kim J.H., Lee W.Y., Hong Y.P., Ryu W.S., Lee K.J., Lee W.S., et al. Psychometric properties of a short self-reported measure of medication adherence among patients with hypertension treated in a busy clinical setting in Korea. J Epidemiol 2014;24:132–40. [42] Ferketich S.. Focus on psychometrics. Aspects of item analysis. Res Nurs Health 1991;14:165–8. [43] Mokkink L.B., Terwee C.B., Patrick D.L., Alonso J., Stratford P.W., Knol D.L., et al. The COSMIN study reached international consensus on taxonomy, terminology, and definitions of measurement properties for health-related patientreported outcomes. J Clin Epidemiol 2010;63:737–45. [44] Mancuso C.A., Peterson M.G., Charlson M.E.. Comparing discriminative validity between a disease-specific and a general health scale in patients with moderate asthma. J Clin Epidemiol 2001;54:263–74. [45] Guyatt G.H., Feeny D.H., Patrick D.L.. Measuring health-related quality of life. Ann Intern Med 1993;118:622–9. [46] Juniper E.F., Guyatt G.H., Ferrie P.J., Griffith L.E.. Measuring quality of life in asthma. Am Rev Respir Dis 1993;147:832–8. [47] Hoffmann T., McKenna K.. Analysis of stroke patients’ and carers’ reading ability and the content and design of written materials: recommendations for improving written stroke information. Patient Educ Couns 2006;60:286–93.
Contents lists available at ScienceDirect
Patient Education and Counseling journal homepage: www.elsevier.com/locate/pateducou
Assessment
Validation of the short-form Health Literacy Scale in patients with stroke Yi-Jing Huang a,1, Yu-Lin Wang b,c,1, Tzu-Yi Wu a, Cheng-Te Chen d, Ken N. Kuo e, Sheng-Shiung Chen f, Wen-Hsuan Hou g,h,i,1,*, Ching-Lin Hsieh a,j,1 a
School of Occupational Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan Rehabilitation Department, Chi Mei Medical Center, Tainan, Taiwan Department of Sports Management, Chia Nan University of Pharmacy and Science, Tainan, Taiwan d Center for Teacher Education, National Tsing Hua University, Hsinchu, Taiwan e Center for Evidence-Based Medicine, Taipei Medical University, Taipei, Taiwan f Department of Physical Medicine and Rehabilitation, E-Da Hospital/I-Shou University, Kaohsiung, Taiwan g Master Program in Long-Term Care, College of Nursing, Taipei Medical University, Taipei, Taiwan h School of Gerontology and Health Management, College of Nursing, Taipei Medical University, Taipei, Taiwan i Department of Physical Medicine and Rehabilitation, Taipei Medical University Hospital, Taipei, Taiwan j Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan b c
A R T I C L E I N F O
A B S T R A C T
Article history: Received 14 July 2014 Received in revised form 12 November 2014 Accepted 20 February 2015
Objective: We aimed to validate a Mandarin version of the short-form Health Literacy Scale (SHEAL) in patients with stroke. Methods: Each patient with stroke was interviewed with the SHEAL. The Public Stroke Knowledge Quiz (PSKQ) was administered as a criterion for examining the convergent validity of the SHEAL. The discriminative validity of the SHEAL was determined with age and education level as independent grouping variables. Results: A total of 87 patients with stroke volunteered to participate in this prospective study. The SHEAL demonstrated sufficient internal consistency reliability (alpha = 0.82) and high correlation with the PSKQ (r = 0.62). The SHEAL scores between different age groups and education level groups were significantly different. The SHEAL, however, showed a notable ceiling effect (24.1% of the participants), indicating that the SHEAL cannot differentiate level of health literacy between individuals with high health literacy. Conclusion: The internal consistency reliability, convergent validity, and discriminative validity of the SHEAL were adequate. However, the internal consistency reliability and ceiling effect of the SHEAL need to be improved. Practice implications: The SHEAL has shown its potential for assessing the health literacy of patients with stroke for research purposes. For clinical usage, however, the SHEAL should be used with caution. ß 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Health literacy Psychometrics Validation Measurement Stroke
1. Introduction Stroke is a chronic disease and has become the leading cause of death and serious, long-term disability globally [1]. More than 7.1% of the world population are affected by stroke annually [1]. To manage chronic diseases and long-term disabilities requires the
* Corresponding author at: Master Program in Long-Term Care, College of Nursing, Taipei Medical University, No. 250, Wuxing St., Xinyi Dist., Taipei City 110, Taiwan. Tel.: +886 2 2736 1661x6311. E-mail address: [email protected] (W.-H. Hou). 1 These authors contributed equally to this paper. http://dx.doi.org/10.1016/j.pec.2015.02.021 0738-3991/ß 2015 Elsevier Ireland Ltd. All rights reserved.
active participation of the patients [2–5], and this can only occur when patients have adequate health literacy [6–9]. Health literacy is defined as the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions [10]. Health literacy is an essential aspect of self-management and shared decision-making to improve health outcomes in patients with stroke. Numerous studies have highlighted the importance of an adequate level of health literacy to the disease management process [11–14] and noted that inadequate health literacy is a potentially modifiable determinant of poor health outcomes in people with chronic disease [15–18]. Thus, it is important to assess
Y.-J. Huang et al. / Patient Education and Counseling 98 (2015) 762–770
the health literacy of stroke survivors early on in order to identify patients at risk of low literacy. Such information is useful for clinicians to ameliorate patients’ health literacy and help them manage their health. Measures of health literacy with sound psychometric properties are a prerequisite to successfully understanding, monitoring, and managing patients’ health literacy. To date, more than a dozen validated measures of health literacy have been developed [19– 21]. Although these measures have been used in several adult or patient populations, their usefulness and applicability for patients with stroke remain unknown. To the best of our knowledge, no measures assessing health literacy have been validated in patients with stroke, which not only hampers clinicians in assessing and understanding the health literacy required for stroke management, but also hinders researchers investigating the concepts of strokespecific health literacy skills. Thus, there is a need to validate existing health literacy measures in patients with stroke, in order to provide clinicians and researchers empirical evidence for assessing and managing health literacy in stroke populations. The short-form Health Literacy Scale (SHEAL) was designed to assess the general population’s comprehension and numeracy skills needed to promote health, seek health care, and manage selfcare [22]. The SHEAL contains 11 items simplified from the Health Literacy Scale [22,23]. The SHEAL is brief and quick to administer (around 5 min), so it could be an efficient measure for assessing health literacy in busy clinical settings [22]. The SHEAL also shows satisfactory psychometric properties (including internal consistency reliability, factorial validity, convergent validity and discriminative validity) in the general public [22]. Hence, the SHEAL is a potential measure for assessing health literacy in patients with stroke. However, the SHEAL has not been validated in patients with stroke. The psychometric properties of a measure are sample dependent [24,25], and all relevant psychometric properties must be examined comprehensively in patient samples to ensure quality of assessment [24]. Consequently, despite the fact that the SHEAL has been validated in the general population, the psychometric findings from the previous study cannot be directly applied to patients with stroke. The psychometric properties of the SHEAL have to be validated in patients with stroke to provide empirical evidence to support its use in these patients. The purpose of this study was to examine the psychometric properties (including internal consistency reliability, convergent validity, and discriminative validity) of the SHEAL in patients with stroke. We hypothesized that the SHEAL would have good internal consistency reliability, as well as sufficient convergent validity and good discriminative validity. 2. Methods
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patient. We excluded patients with aphasia or severe cognitive impairments (Mini-Mental State examination score <22 [27]) who had difficulty completing the interview and providing reliable responses. This study received approval from the ethical review committees of the two hospitals. 2.2. Procedures We used convenience sampling to recruit subjects who were accessible and eligible. After being referred to the interviewer by therapists, potential and accessible subjects were invited to participate in this study. Subjects who agreed to participate in this study received screening tests to determine eligibility. Eligible subjects were interviewed face-to-face by an experienced research assistant with a Mandarin version of the SHEAL and a Mandarin version of the Public Stroke Knowledge Quiz (PSKQ). A set of questions regarding demographic data and stroke related information was completed by participants or obtained from their medical charts. During the interview, the patient’s family members could stay by the patient’s side but could not actively influence the patient. 2.3. Measure The Mandarin version of the SHEAL assesses adults’ health literacy in terms of their ability to read, comprehend, and utilize basic health information in making personal health decisions [22]. The SHEAL was simplified from the Health Literacy Scale, which was developed based on the definition of health literacy proposed by the Institute of Medicine (2004) and the National Research Council (2005), and comprises questions regarding prose, document, and numeracy skills [10,23,28]. The SHEAL contains 11 multiple-choice items, of which 8 test comprehension (prose and document) abilities and 3 assess numeracy skills. Each correct response receives 1 point; incorrect responses receive 0 points. The total score ranges from 0 to 11. Higher scores indicate better health literacy. The Mandarin version of the PSKQ [29] was designed by the Taiwan Stroke Association to assess knowledge of stroke among the general public. We chose the PSKQ as the criterion to estimate the convergent validity of the SHEAL. The selection was based on previous studies that showed a significant correlation between health literacy and health knowledge [12,30,31]. The quiz comprises 10 true/false items and 10 multiple-choice items that evaluate basic stroke-related knowledge, including prevention, warning signs, symptoms, emergency response, treatment, and prognosis of stroke. An incorrect answer for each item is scored as 0 and a correct answer is scored as 1. The total score ranges from 0 to 20. Higher scores indicate higher levels of stroke knowledge.
2.1. Participants 2.4. Statistical analysis This study was conducted between July 1 2013, and October 31 2013. Although there are no commonly accepted methods for calculating the required sample size in a psychometric study, a sample size of at least 50–100 subjects is generally recommended [26]. Subjects were recruited from the rehabilitation departments of two teaching hospitals in northern Taiwan. Patients were invited to participate in the study if they met the following criteria: (1) diagnosis (International Classification of Diseases, Ninth Revision, Clinical Modification codes) of cerebral hemorrhage (431), cerebral infarction (434), or others (430, 432, 433, 436, 437) with stroke symptoms (e.g., hemiparesis or hemiplegia) confirmed by a neurologist, (2) age 20 years, (3) ability to complete the interview and to provide reliable outcomes as judged by the interviewer, and (4) written informed consent for participation obtained from the
We analyzed the distribution of the demographic characteristics of participants, the distribution of the SHEAL scores, and the internal consistency reliability and validity (convergent validity and discriminative validity) of the SHEAL. The floor and ceiling effects, the percentages of the sample scoring the minimum and maximum possible scores, respectively, reflect the extent to which scores cluster at the bottom and top of the scale range. Floor and ceiling effects >15% were considered to be significant [32]. The internal consistency reliability of the SHEAL was determined by Cronbach’s alpha. An alpha coefficient greater than 0.70 was considered adequate for group comparison (e.g., using the SHEAL scores for a group of participants, commonly for research
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purposes), while a coefficient greater than 0.90 was considered adequate for individual comparison (e.g., using the SHEAL score for a patient in a clinical setting) [33]. We also conducted item analysis by examining the mean inter-item correlation and corrected itemtotal correlation of each item in the SHEAL. It is recommended that the mean inter-item correlation exceed 0.30 [34], and that the corrected item-total correlation exceed 0.40 [35]. To estimate the convergent validity of the SHEAL, we examined the strength of the correlation between the SHEAL scores and the scores of the PSKQ using the Pearson correlation coefficient. An r coefficient >0.60 indicates high convergent validity; 0.30–0.60, moderate; and <0.30, poor [36]. To examine the discriminative validity of the SHEAL, we selected two variables—age and education level—because of previous evidence showing that health literacy was significantly related to age and educational attainment [18,31,37,38]. The ability of the SHEAL to discriminate between groups of participants was investigated by comparing mean scores between middle-aged and elderly participants (<60 and 60 years old) and between 2 education level groups (<10 and 10 years of formal education) using two-way analysis of variance (ANOVA). All statistical analyses were conducted using SPSS 15.0 Software (SPSS Inc., Chicago, IL, USA). Two-sided p < 0.05 was considered statistically significant. 3. Results 3.1. Demographics of the participants A total of 87 (54% male) patients with stroke joined this study. The average age of the participants was 57 years. The majority of
Gender Male Female Age Years of formal educationa 1–6 7–12 13–16 17 Occupation Retired Unemployed Labor Manager Urbanization level of residencea Moderately to highly urbanized cities Developing cities Rural areas Sources of patients Outpatients Inpatients Types of stroke Hemorrhagic Ischemic Others Months after strokea <6 months (subacute stage) 6 months (chronic stage) Affected side Left Right Both Modified Rankin Scale Public Stroke Knowledge Quiz Short-form Health Literacy Scale a
Mean (SD)
n (%) 47 (54.0%) 40 (46.0%)
57.4 (15.1) 20 12 30 3
(23.0%) (13.8%) (34.5%) (3.4%)
37 32 15 3
(42.5%) (36.8%) (17.2%) (3.4%)
64 (73.6%) 12 (13.8%) 7 (8.0%) 77 (88.5%) 10 (11.5%) 31 (35.6%) 52 (59.8%) 4 (4.6%) 21.3 (25.8) 24 (27.6%) 55 (63.2%) 54 (62.1%) 29 (33.3%) 4 (4.6%) 2.5 (1.1) 13.3 (3.1) 8.1 (2.8)
Total percentages do not add up to 100 due to missing values.
the participants were outpatients with chronic stroke (6 months post stroke) and diagnosed as ischemic stroke (63.2% and 59.8%, respectively). The average duration after stroke of the participants was 21 months. Most of the participants had 10–16 years of formal schooling (senior high to college) and lived in urbanized cities. Other demographic characteristics of the stroke patients are shown in Table 1. 3.2. Distribution of the SHEAL scores
Table 1 Demographic characteristics of the participants (n = 87). Variable
Fig. 1. Histogram with normal curve superimposed over the distribution of total scores of the short-form Health Literacy Scale.
The mean SHEAL score was 8.1 in the study sample. Fig. 1 shows the distribution of the SHEAL scores. In examining the floor and ceiling effects of the SHEAL, we found that 1% of the patients obtained the lowest score of the SHEAL and 24% of them obtained the highest score. Furthermore, regardless of time after stroke onset, more than 15% of the participants reached the highest score (20.8% and 23.6% for subacute stage and chronic stage, respectively). 3.3. Psychometric properties of the SHEAL With regard to the internal consistency reliability of the SHEAL, the alpha value was 0.82, which was higher than the criterion of 0.70 for group comparison but lower than that of 0.90 for individual comparison. Table 2 presents the results of item
Table 2 Results of item analysis of the SHEAL. Item number and item content
Mean inter-item correlation
Corrected item-total correlation
Cronbach’s alpha if item deleted
1. Symptom expression 2. Drug applications 3. Medical tests 4. Disease management 5. Patient name 6. Medication time 7. Medication frequency 8. Drug dosage 9. Prescription duration 10. Side effects 11. Precautions
0.25a 0.20a 0.12a 0.19a 0.37 0.33 0.29a 0.39 0.35 0.32 0.40
0.42 0.31b 0.18b 0.25b 0.62 0.58 0.46 0.67 0.61 0.54 0.70
0.82 0.82 0.83 0.82 0.80 0.80 0.81 0.79 0.80 0.80 0.79
a b
The mean inter-item correlation was below 0.30. The corrected item-total correlation was below 0.40.
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Fig. 2. Differences in the short-form Health Literacy Scale scores among different age and education level groups.
analysis. Among the 11 items in the SHEAL, items 2–4 showed both inadequate mean inter-item correlations and poor corrected itemtotal correlations. When these three less relevant items were removed from the SHEAL, Cronbach’s alpha increased from 0.82 to 0.85. Correlation between the scores of the SHEAL and that of the PSKQ was 0.62 (p < 0.001), indicating that the two scales were highly correlated. In terms of the discriminative validity (Fig. 2), a two-way ANOVA revealed significant age (F1, 80 = 7.79, p = 0.007) and education effects (F1, 80 = 5.49, p = 0.022) but no significant interaction between age and education (F1, 80 = 0.12, p = 0.73). 4. Discussion and conclusion 4.1. Discussion This study, to the authors’ knowledge, is the first to investigate the psychometric validity of the SHEAL in patients with stroke. Owing to the lack of health literacy measures validated in stroke survivors, no health literacy measures with robust psychometric evidence can be used in a stroke population. The findings of this study can provide psychometric evidence of the SHEAL for both clinicians and researchers to assess health literacy in patients with stroke. 4.1.1. Distribution of the SHEAL scores A floor/ceiling effect means a measure cannot differentiate between individuals with low/high levels of an underlying trait, respectively [32]. The SHEAL demonstrated no floor effect and a significant ceiling effect in patients with stroke. The results indicate that the SHEAL is able to discriminate the health literacy of individual patients with low health literacy but not able to distinguish that of individual patients with high health literacy. The ceiling effect of the SHEAL might be attributed to the fact that patients with stroke often have other chronic diseases (e.g., hypertension, diabetes mellitus) and have to receive long-term medication. These facts might have made the chronic patients more likely to be familiar with the items regarding physicianspatients dialogues in the outpatient clinics and prescription labels in the SHEAL. However, our results showed that regardless of time after stroke, the SHEAL had notable ceiling effects both in the participants with subacute stroke and in those with chronic stroke. Furthermore, a notable ceiling effect of the SHEAL (43.2% of a healthy adult sample received the highest score) was also found in a validation study [22]. These observations indicate that the items
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on the scale may be too easy for a high proportion (24.1%) of the participants with stroke, thus allowing their scores to cluster at the upper limit of the SHEAL. The SHEAL with a significant ceiling effect would have the following two flaws when it is administered in patients with higher level of health literacy. First, patients obtaining the highest possible score of the SHEAL does not necessarily imply a positive correlation with a high level health literacy - it may for example mean that the items in the SHEAL are not very challenging. Second, the ceiling effect limits the SHEAL’s ability to detect improvements in the health literacy of patients with scores clustered at the top of the scale [36,39]. In order to promote the utility of the SHEAL, it would be necessary to minimize the ceiling effect. Revising the scale by adding more challenging items (e.g., items assessing the abilities to calculate and comprehend graphs) may be warranted. However, it is noted that when the health information providers’ main concerns are patients with low health literacy, the ceiling effect of the SHEAL should be less problematic. 4.1.2. Internal consistency reliability Internal consistency reliability refers to the consistency among responses to the items within a measure [40]. Our results (alpha = 0.82) showed sufficient internal consistency reliability in the SHEAL, which means that the 11 items of the SHEAL are homogeneous in measuring stroke patients’ health literacy. In addition, the obtained alpha value might be an underestimate for the following two reasons: (1) the ceiling effect lowered the variability in the SHEAL scores, which would compromise the internal consistency reliability [41]; and (2) the 11 items of the SHEAL are dichotomous items, which tended to undervalue the strength of correlation and then decreased the alpha value [41]. Thus, the high level of internal consistency reliability (alpha = 0.82) reasonably suggests that the SHEAL is a reliable scale and is satisfactory for group comparison (i.e., research application). Through item analysis, however, we found that three items (items 2–4) had low correlations both with the other items and with the total scores of the SHEAL. These findings imply that the participants’ responses to the three items were less consistent as compared to those of the other items, and that they had lowered the alpha coefficient in this study [42]. Thus, to improve the internal consistency reliability of the SHEAL for individual comparisons (i.e., clinical application) in a stroke population, it would be necessary to drop the less relevant items and add more highly reliable items in the future. 4.1.3. Convergent validity Convergent validity represents the degree to which the construct of a measure assessing is correlated with the other construct(s) that are theoretically related [43]. The scores of the SHEAL were highly correlated with those of the PSKQ (Pearson’s r = 0.62). This result is consistent with previous studies demonstrating that health literacy is correlated with health knowledge [12,30,31]. In addition, because the ceiling effect of the SHEAL limited the variability in the scores, the correlation obtained is quite possibly an underestimate of the true magnitude of the correlation. Therefore, the high correlation supports the convergent construct validity of the SHEAL. 4.1.4. Discriminative validity Discriminative validity of a measure provides information on how well a measure differentiates, as expected, between participant groups who differ in their underlying trait [44,45]. Our results showed that given the same education level group, the SHEAL scores of the older participants were significantly lower than those of the younger participants; on the other hand, given the same age group, the SHEAL scores of participants with lower education levels were significantly lower than those of participants with
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higher education levels. These findings indicate that the SHEAL was able to uncover differences in health literacy between disparate age and educational attainment groups of patients with stroke. These results suggest that the SHEAL, having good discriminative validity, is useful for comparing patients’ health literacy levels in cross-sectional studies [46]. It can also assist clinicians in distinguishing between groups of patients with higher and lower health literacy, which may be useful for clinicians to identify patients needing early health literacy intervention [44]. 4.1.5. The SHEAL scores of the stroke patients The mean SHEAL score (8.1) in the study sample was somewhat lower than that of healthy adults in a previous survey (9.0) [22]. Our results demonstrated that the psychometric properties of the SHEAL are sound in patients with stroke. Such results may give us support to explain that the relatively low scores on the SHEAL represent the relatively low level of health literacy in the stroke patients as compared with that of healthy adults. Similar findings were reported in a previous study, which demonstrated that the average level of health literacy of patients following stroke was lower than that of their caregivers (indicative of healthy adults) [47]. These findings imply that stroke patients are more likely to have difficulty in dealing with health-related activities, such as communicating with clinicians and understanding prescriptions or instructions. 4.1.6. Limitations Four sampling issues may have threatened the external validity of this study. First, our participants were a convenience sample. Second, most of the participants were outpatients with chronic stroke and lived in moderately to highly urbanized cities, which might have caused a sampling bias in terms of time after stroke and place of residence. Third, our eligibility criteria excluded people who could not follow instructions to complete the assessment. Last, the size of the sample in our study was not large. Thus, the results should be cautiously generalized to patients at acute and subacute stages, as well as stroke patients with severe cognitive impairment or aphasia. Furthermore, the psychometric properties of the PSKQ are largely unknown, which might have threatened the internal validity of the findings. In addition, although this study provides preliminary support for the use of the SHEAL in patients with stroke, we did not examine the test-retest reliability, concurrent validity, factorial validity or responsiveness of the SHEAL. Further examination of the aforementioned properties is
needed to fully demonstrate the psychometric properties and utility of the SHEAL in patients with stroke. 4.2. Conclusions Our results support the internal consistency reliability, convergent validity and discriminative validity of the SHEAL in measuring health literacy in patients with stroke. However, we found that the SHEAL had a limited ability to distinguish between individuals with high levels of health literacy among stroke patients. To promote the utility of the SHEAL, it will be necessary to minimize the ceiling effect and to increase the internal consistency reliability of the scale. Further revision of the SHEAL is warranted; more challenging items should be added and less relevant items should be deleted. 4.3. Practice implications For future investigation of health literacy for patients with stroke, the SHEAL appears to be a valid and reliable measure. Our results lend support for the usage and further investigation of health literacy in patients with stroke. However, clinicians should apply the SHEAL with caution because the SHEAL might not be very precise for measuring health literacy in individual stroke patients, and the SHEAL might be too easy for some patients with high levels of health literacy. Conflicts of interest The authors have no conflicts of interest relevant to this article. Informed consent and patient details I confirm all patient/personal identifiers have been removed or disguised so the patient/person(s) described are not identifiable and cannot be identified through the details of the story. Acknowledgements This study was supported by research grants from the Taipei Medical University (TMU101-AE1-B21), Chi Mei Medical Center (103CM-TMU-12), E-Da Hospital (EDAHT103019), Ministry of Science and Technology (102-2314-B-038-007-MY3) and National Health Research Institutes (NHRI-EX102-10207PI).
Appendix: The short-form Health Literacy Scale
Part 1: Physician-patient Dialogues in outpatient clinics The following items are simulated conversations with your doctor at the clinic. Please choose the most appropriate answer from the options according to the description of each item. (
) 1.
Doctor, my right big toe has been painful for 4-5 days. It gets more and more painful and _____. The pain hasn’t been relieved at all. (1) obese (2) swollen (3) dehydrated
Y.-J. Huang et al. / Patient Education and Counseling 98 (2015) 762–770
( ) 2.
Paronychia is a kind of tissue inflammation. I’ll prescribe some _____ for you in order to relieve the pain and swelling. (1) antibiotics (2) antihypertensive drugs (3) hormones
(
) 3.
Have you had diabetes? At the next visit, please _____ and take this blood examination sheet to do a blood test at the department of laboratory medicine. (1) hold your urine (2) fast (3) eat
( ) 4.
After returning home, don’t wear shoes that are _____ temporarily. Keep your foot dry and breathable. If it doesn’t worsen, consult outpatient follow up after 5 days. (1) too tight (2) too soft (3) too loose
Part 2: Prescription Labels Date Dispensed Oct. 10, 2007
Prescription No.
N-0034
Patient Name
Da-Tong Li
History No.
25688652
Birthday
May 28, 1967
Gender
Male
Administration
Oral once a day 30 minutes before breakfast
Dosage
1/2 tablet each time
Drug Name
Euglucon 5 mg / tablet
Duration
14 days
Composition
Glyburide
Quantity
7 tablets
Appearance
tablet
Clinical Uses
Increase insulin secretion to lower blood sugar
Side effects
May cause low blood sugar (cold sweats, palpitations, headaches,
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shakiness, dizziness), fever, sore throat, skin rash, jaundice, etc. Precautions
Avoid driving or operating heavy machinery until your blood sugar level is stable. Do not drink alcohol while taking this drug. Please take sunburn protection measures.
Physician
Yi-Lin Wang
Dispensing Pharmacist
Zhong-Xin Lin
Verifying Pharmacist
Da-Ming Li
Please answer the following questions and choose the most appropriate option according to the contents of the prescription: (
) 5.
What is the name of the patient who takes this drug? (1) Yi-Lin Wang (2) Da-Tong Li (3) Zhong-Xin Lin
(
) 6.
When should the patient take this drug? (1) 30 minutes before meals (2) 30 minutes before sleep (3) 30 minutes after meals
(
) 7.
If the patient took this drug before breakfast today, it is better to take the next dose _____. (1) before dinner today
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(2) before breakfast tomorrow (3) before lunch tomorrow (
) 8.
How many drugs should the patient take each time? (1) 1/2 tablet (2) 1 tablet (3) 5 tablets
(
) 9.
The physician prescribed a total course of _____ days. (1) 1 (2) 7 (3) 14
(
) 10.
Taking this drug may cause side effects associated with low blood sugar, such as symptoms of _____. (1) skin rash (2) jaundice (3) palpitations
(
) 11.
Patients taking this drug should avoid driving or operating heavy machinery until their _____ level is stable. (1) blood pressure (2) blood sugar
(3) urinary protein
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