Comparison of the psychometric properties of four at-work disability measures in workers with shoulder or elbow disorders.

Introduction: To better capture the extent of work disability following an occupational injury, clinical researchers are beginning to recognize the importance of considering not only levels of absenteeism, but also disabilities experienced while "at-work". Although at-work disability measures are available in the literature, currently there is little insight on the selection of specific measures that may be best suited for a given population or situation. The objective of this study is to assess and compare the measurement properties of four self-report at-work disability measures in workers with shoulder or elbow disorders.

Methods: Study sample consisted of 80 patients attending a shoulder and elbow specialty clinic operated by the Worker Safety Insurance Board of Ontario. Internal consistency reliability, validity, and patient preference of four at-work disability measures were compared in a cross-sectional design. Selected measures included the work module of the Disabilities of the Arm, Shoulder and Hand Outcome Measure, Work Limitations Questionnaire (WLQ-16), Work Instability Scale for Rheumatoid Arthritis (RA-WIS), and Stanford Presenteeism Scale.

Results: All four measures demonstrated evidence of internal consistency reliability (alpha = 0.76-0.90) and construct validity, although only modest correlations against work-oriented constructs (r = 0.37-0.60) were observed. The RA-WIS was most preferred by respondents (44.6%) over the other measures.

Conclusions: Although no single scale stood out as clearly superior, the WLQ-16 was considered the best overall performer. Variable performance between the scales suggests some divergence in the way these measures conceptualize "at-work disability", which may be important to consider when selecting instruments for future studies.