Background/Purpose: There are a number of single item global measures available to explore at-work productivity loss (presenteeism) in patients with rheumatological conditions.  However, test-retest data are not available for all these measures and comparison data are lacking. The purposes of this study were i) to test-retest five at-work productivity loss global measures, including: Work Productivity Scale – Rheumatoid Arthritis (WPS-RA), Work Productivity and Activity Impairment Questionnaire (WPAI), Work Ability Index (WAI), Quality and Quantity questionnaire (QQ),and WHO Health and Performance Questionnaire (HPQ), ii) to explore the correlations between the 5 measures, and iii) to investigate the association between the 5 scales and disease activity.

Methods: In this international study 50 patients with a diagnosis of inflammatory arthritis or osteoarthritis in paid employment were recruited from 7 countries (United Kingdom, Sweden, France, The Netherlands, Romania, Italy, and Canada).  At baseline and 2 wk follow up, participants completed the five 10-point global measures (WPAI; 0=no effect on work – 10=completely prevented from working, WPS-RA; 0=no interference – 10=complete interference, WAI; 0=unable to work – 10=work ability at its best, QQ; 0= practically nothing/very poor quality – 10=normal quantity/very good quality, HPQ; 0=worst performance – 10=top performance).  VAS general well-being was also recorded at 2 wks.  Test-retest reliability was assessed applying intra-class correlation (ICC) statistics.  ICCs of 0.75 and 0.95 are generally regarded as good at respectively group and individual level.  Spearman correlations were calculated to determine the association between the two week global scores and between each scale with the VAS general well-being score.

Results:   54% of the study population was female; mean age was 44 (SD 10.2) yrs and median symptom duration 9.5 [IQR 5-15] yrs.  Median VAS general well-being was 28 [IQR 12-55].  72% of the study population had a non-manual occupation. ICC correlations were moderate at a group level: WPAI (r=0.65), WPS-RA (r=0.66), WAI (r=0.81), QQ-quantity (r=0.70), QQ-Quality (r=0.68) and HPQ (r=0.62).  The correlations between the 5 at-work productivity measures ranged from good (WPS-RA vs WPAI, r=0.92) to moderate (QQ-quality and QQ-quantity with all 4 other measures) (see table).  Correlations between each of the individual measures and VAS general well-being were low to moderate.

Conclusion: Overall, test-retest results of the 5 existing at-work productivity loss measures and the correlation between these 5 measures were moderate. The latter probably reflecting differences in concepts, recall periods, and references used in these measures.  The moderate association between the global at-work productivity measures and VAS general well-being suggests that the impact of arthritis on work is only partly captured by generic health measures.