VALIDATION OF THE CROATIAN VERSION OF WORK ABILITY INDEX (WAI) IN POPULATION OF NURSES ON TRANSFORMED ITEM-SPECIFIC SCORES

Aim: To assess the psychometric properties of the Croatian version of a Work Ability Index Questionnaire (WAIQ-CRO) in the population of nurses by using a specific methodological approach. Methods: A cross-sectional survey was conducted in a sample of 711 Croatian nurses in 2018 in Zagreb, Croatia. The instrument's internal consistency was assessed by using Cronbach's alpha coefficient (alpha). The factor structure was verified by confirmatory (CFA) and exploratory factor analysis (EFA), with the assumption of a single-factor structure. To ensure the equality of importance of items in the assessment, the item-specific scores were transformed. Results: The internal consistency of the instrument was satisfactory (alpha=0.71). CFA showed poor first model (Model-1) compatibility data (p<0.001, CFI=0.85, GFI=0.93, RMSEA=0.13). The modificated indexes suggested the introduction of correlation parameters residual variances of results from WAIQ-CRO Item-1 and Item-2. After introducing these covariances, the index model assentation (Model-2) showed desirable assentation measures (p<0.001, CFI=0.95, GFI=0.97, RMSEA=0.08). Comparison showed better compatibility of Model-2 (p<0.001). The implementation of EFA has identified three factors. Replication of this model in CFA resulted in relatively good model assentation approaches with data (p<0.001, CFI=0.96, GFI=0.98, RMSEA=0.07). Comparison of this model (Model-3) with Model-2 showed a significantly better compatibility of Model-3 (p<0.001). Conclusion: The WAIQ-CRO proved to be a reliable and valid instrument which can be used in research among Croatian nurses. The results suggest that it would be better to consider a three-factor structure than a single-factor structure, as a three-factor structure can direct decision-makers to which segment to locate interventions.