The psychometric properties of an Iranian translation of the Work Ability Index (WAI) questionnaire.
ABSTRACT This study was carried out to evaluate the psychometric properties of an Iranian translation of the Work Ability Index (WAI) questionnaire.
In this methodological study, nurses and healthcare workers aged 40 years and older who worked in educational hospitals in Ahvaz (236 workers) in 2010, completed the questionnaire and 60 of the workers filled out the WAI questionnaire for the second time to ensure test-retest reliability. Forward-backward method was applied to translate the questionnaire from English into Persian. The psychometric properties of the Iranian translation of the WAI were assessed using the fallowing tests: Internal consistency (to test reliability), test-retest analysis, exploratory factor analysis (construct validity), discriminate validity by comparing the mean WAI score in two groups of the employees that had different levels of sick leave, criterion validity by determining the correlation between the Persian version of short form health survey (SF-36) and WAI score.
Cronbach's alpha coefficient was estimated to be 0.79 and it was concluded that the internal consistency was high enough. The intraclass correlation coefficient was recognized to be 0.92. Factor analysis indicated three factors in the structure of the work ability including self-perceived work ability (24.5% of the variance), mental resources (22.23% of the variance), and presence of disease and health related limitation (18.55% of the variance). Statistical tests showed that this questionnaire was capable of discriminating two groups of employees who had different levels of sick leave. Criterion validity analysis showed that this instrument and all dimensions of the Iranian version of SF-36 were correlated significantly. Item correlation corrective for overlap showed the items tests had a good correlation except for one.
The finding of the study showed that the Iranian version of the WAI is a reliable and valid measure of work ability and can be used both in research and practical activities.
- Scandinavian journal of work, environment & health 02/2009; 35(1):1-5. · 3.78 Impact Factor
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ABSTRACT: This was a large population-based study to develop and validate the Iranian version of the Short Form Health Survey (SF-36) for use in health related quality of life assessment in Iran. A culturally comparable questionnaire was developed and pilot tested. Then, the Iranian version of the SF-36 was administered to a random sample of 4163 healthy individuals aged 15 years and over in Tehran. The mean age of the respondents was 35.1 (SD = 16.0) years, 52% were female, mostly married (58%) and the mean years of their formal education was 10.0 (SD = 4.5). Reliability was estimated using the internal consistency and validity was assessed using known groups comparison and convergent validity. In addition factor analysis was performed. The internal consistency (to test reliability) showed that all eight SF-36 scales met the minimum reliability standard, the Cronbach's alpha coefficients ranging from 0.77 to 0.90 with the exception of the vitality scale (alpha = 0.65). Known groups comparison showed that in all scales the SF-36 discriminated between men and women, and old and the young respondents as anticipated (all p values less than 0.05). Convergent validity (to test scaling assumptions) using each item correlation with its hypothesized scale showed satisfactory results (all correlation above 0.40 ranging from 0.58 to 0.95). Factor analysis identified two principal components that jointly accounted for 65.9% of the variance. In general, the Iranian version of the SF-36 performed well and the findings suggest that it is a reliable and valid measure of health related quality of life among the general population.Quality of Life Research 05/2005; 14(3):875-82. · 2.41 Impact Factor
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ABSTRACT: The goal of the study was to assess the test-retest reliability of the Work Ability Index (WAI) questionnaire. Reliability was tested using a test-retest design with a 4 week interval between measurements. Valid data were collected among 97 elderly construction workers aged 40 years and older. We analysed the test-retest reliability of the WAI score itself (range 7-49 points) and classification in one of the four WAI categories based on this score: poor (7-27 points); moderate (28-36 points); good (37-43 points); and excellent work ability (44-49 points). Exactly the same WAI score on both measurements was reported by 25% of the subjects and 95% of the individual differences between measurements were found to be <6.86 points (two times standard deviation). Despite the individual changes between measurements, no significant difference was reported in the mean WAI score at group level between test and retest measurements (40.4 versus 39.9). The percentage of observed agreement for the classification of subjects in one of the four WAI categories on both measurements equalled 66%. The results of this study provided evidence of an acceptable test-retest reliability of the classification of subject's work ability by means of the WAI questionnaire. At group level, the mean WAI score and classification into WAI categories were found to be a stable measure over a 4 week interval. These results give additional support for the applicability of the questionnaire in occupational health research and the daily practice of occupational health care.Occupational Medicine 06/2002; 52(4):177-81. · 1.45 Impact Factor