Validity and reliability of work ability index (WAI) questionnaire among Iranian workers; a study in petrochemical and car manufacturing industries.

Maintenance and promotion of employees' work ability is one of the important social goals. This study is aimed at investigating psychometric properties of the Persian translation of work ability index (WAI). A total number of 750 employees were randomly selected from car manufacturing and petrochemical industries. Reliability of the questionnaire was determined using test-retest and Cronbach alpha coefficient. Factor analysis was used for assessing construct validity. To determine discriminant validity, the mean score of total WAI was compared between workers with high and low sick leave rate. Intraclass correlation coefficients for its seven dimensions were estimated higher than 0.7. The questionnaire showed a good internal consistency, Cronbach α = 0.78. Factor analysis showed a three-factor structure model for Persian translation of WAI including: mental resources, self-perceived work ability, and presence of disease and health-related limitation. A good level of discriminant validity was observed for all WAI dimensions except the item "work ability regarding work demands." The study findings indicate that the Persian version of WAI questionnaire has good psychometric properties of internal consistency and test-retest showed a good reliability of WAI questionnaire, which is in line with those found in previous studies. Therefore, this tool can be considered as a reliable instrument for assessing work ability.

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© 2019 The Authors. Journal of Occupational Health published by John Wiley & Sons Australia, Ltd on behalf of The Japan Society for Occupational Health.