Test-retest Reliability and Correlations of 5 Global Measures Addressing At-work Productivity Loss in Patients with Rheumatic Diseases.

OBJECTIVE: Several global measures to assess at-work productivity loss or presenteeism in patients with rheumatic diseases have been proposed, but the comparative validity is hampered by the lack of data on test-retest reliability and comparative concurrent and construct validity. Our objective was to test-retest 5 global measures of presenteeism and to compare the association between these scales and health-related well-being. METHODS: Sixty-five participants with inflammatory arthritis or osteoarthritis in paid employment were recruited from 7 countries (UK, Canada, Netherlands, France, Sweden, Romania, and Italy). At baseline and 2 weeks later, 5 global measures of presenteeism were evaluated: the Work Productivity Scale-Rheumatoid Arthritis (WPS-RA), Work Productivity and Activity Impairment Questionnaire (WPAI), Work Ability Index (WAI), Quality and Quantity questionnaire (QQ), and the WHO Health and Performance Questionnaire (HPQ). Agreement between the 2 timepoints was assessed using single-measure intraclass correlations (ICC) and correlated between each other and with visual analog scale general well-being scores at followup by Spearman correlation. RESULTS: ICC between measures ranged from fair (HPQ 0.59) to excellent (WPS-RA 0.78). Spearman correlations between measures were moderate (Qquality vs WAI, r = 0.51) to strong (WPS-RA vs WPAI, r = 0.88). Correlations between measures and general well-being were low to moderate, ranging from -0.44 ≤ r ≤ 0.66. CONCLUSION: Test-retest results of 4 out of 5 global measures were good, and the correlations between these were moderate. The latter probably reflect differences in the concepts, recall periods, and references used in the measures, which implies that some measures are probably not interchangeable.