Objective (s): To evaluate the psychometric properties of the Persian version of Work Ability Index questionnaire (WAI).Methods: In this methodological study, a sample of nurses and healthcare staff aged 40 years and above working in educational hospitals in Ahvaz (236 workers) in 2010, completed the questionnaire. Forward-backward method was applied to translate the questionnaire from English into Persian. The psychometric properties of Persian version of the WAI were assessed using the

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... ng tests: Internal consistency and test-retest analysis (to test reliability), exploratory factor analysis, discriminant validity and convergent validity by determining the correlation between the Persian version of Short Form Health Survey (SF-36) and WAI score.Results: The Cronbach's alpha coefficient was estimated to be 0.79 and the ICC was 0.83. Factor analysis indicated three factors: 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 the questionnaire was capable of discriminating two groups of employees who had different levels of sick leave. Convergent validity analysis showed that the instrument significantly correlated with all dimensions of Persian version of SF-36. Item-scale correlation corrected for overlap showed the items had a good correlation except for item.Conclusion: The finding showed that the Persian version of Work Ability Index is a reliable and valid measure of work ability and can be used both in research and practice.