Reproducibility of work ability and work functioning instruments

Work ability (WA) and work functioning (WF) instruments can be useful in occupational health practice. The reproducibility of both instruments is important to their relevance for daily practice. Clinimetrics concerns the methodological and statistical quality of instruments and their performance in practice.

To assess the reproducibility of WA and WF instruments.

Dutch workers completed a questionnaire containing WA questions and the WF questionnaire twice with a 7-day interval between. The questionnaire included an appraisal of current general, physical and mental/emotional WA (0-10) and the composite WF questionnaire of 49 items (0-100). We measured reproducibility, reliability and agreement by calculating the intraclass correlation coefficient (ICC), the standard error of measurement (SEM) and the smallest detectable change (SDC).

The answers of 104 respondents were available for analysis. General, physical and mental/emotional WA had ICC values of 0.52, 0.69 and 0.56, respectively. For WF, the ICC value was 0.85. For general WA, the SEM was 0.71. For physical and mental/emotional WA, the SEMs were 0.75 and 0.74, respectively. For general, physical and mental/emotional WA, the SDC was 1.98, 2.09 and 2.05 respectively. The SEM of the WF score was 4.78, and the SDC was 13.25.

The WA questions showed moderate reliability, while the WF instrument showed good reliability. Occupational health professionals can use the SDCs of the instruments to monitor changes in WA and WF in workers over time.