A critical look at measurement of work outcomes for people with arthritis
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STUDY ONE Objective. To evaluate the methodological quality of studies examining psychometric properties of work outcome assessments for people with arthritis to guide instrument selection use based on quality of literature. Methods. A systematic review was conducted through a structured search to identify articles describing studies of assessment development and studies of their psychometric properties. The COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist was used to appraise the included studies. Finally, an evidence synthesis was performed to combine findings. Results. Nine arthritis specific work outcome assessments were identified; 17 articles examining the psychometric properties of these instruments were identified and reviewed. Quality of studies reporting psychometrics of each instrument was highly variable. The evidence synthesis showed that the Work Limitations Questionnaire had the strongest quality evidence of internal consistency and content validity (including structural validity and hypothesis testing), followed by the Work Instability Scale. None of the instruments had strong quality evidence of criterion validity or responsiveness. Conclusion. Considering the high variability and the low quality of the literature, we recommend that instrument developers integrate studying full psychometric assessment of their instruments, including responsiveness and criterion validity, and consult guidelines (i.e. COSMIN) in reporting their findings. STUDY TWO Background. The World Health Organization – Health and Work Performance Questionnaire (HPQ) was developed to ascertain absence from work and reduced work performance in the workplace due to health problems. The purpose of this study is to evaluate the construct validity and scoring methods of the work performance subscale of the HPQ for people with arthritis. Methods. Cross-sectional data from a randomized clinical trial on preventing work limitations was used. Construct validity of work performance was examined through hypothesis testing using convergence and divergence based on established risk factors from the literature. Pearson’s correlations were used for continuous data, and Spearman’s Ranked correlations for categorical data were used to test the hypotheses. Both scoring methods of the HPQ (absolute and relative) were evaluated. Results. Data from 287 participants showed that the sample had moderate levels of limitations in work performance. The HPQ showed acceptable construct validity through convergence and divergence. The absolute scoring method had more significant and stronger associations than the relative scoring method. Conclusion. This study was the first exploring the construct validity of the HPQ for people with arthritis, and since construct validity is a continuing process, more research is needed to further assess the ability of the HPQ to measure work performance. One scoring method (i.e. absolute) was more informative that the other. More research is needed to explore other psychometric properties of the HPQ such as responsiveness and test-retest reliability.