EVALUATION OF A DECRESE IN WORK PRODUCTIVITY IN PATIENTS WITH RHEUMATOID ARTHRITIS

Objective. To study the association between the clinical manifestations and work ability in patients with rheumatoid arthritis (RA) and to elaborate mathematical methods for predicting work productivity indicators according to the evaluation of the functional status of patients and disease activity.
Material and Methods. A total of 185 RA patients were examined; 105 of them were employed. The mean age was 48.2±11.3 years; RA duration was 77.9±70.7 months; DAS28 4.68±1.53; visual analogue scale (VAS) score was 40.6±22.2; HAQ was 1.3±0.7. The employed patients in the test group had a longer duration but weaker activity of RA according to DAS28 as compared to those in the control group (p<0.05). The WPAI indicators in the test and control groups, respectively, were as follows: presenteeism – 39.0±26.3 vs. 57.9±16.8%; total productivity decrease (TPD) – 54.6±34.1 vs. 65.2±23.3%; daily activity (DA) – 52.3±26.3 vs. 55.3±14.8%. The multiple regression method was used to create prognostic equations. A significant divergence of the distribution of absenteeism rates from the normal distribution prevented selection of regression equations.
Results. HAQ, VAS pain, and DAS28 turned out to be optimal for selecting equations. The Spearman correlation coefficients with WPAI indicators were higher than 0.4 in all the cases. The following prognostic equations were obtained:
Presenteeism (%) = 0.66 + 11.31 • HAQ + 0.44 • VAS pain + 2.17 • DAS28 (R2 = 0.46),
TPD (%) = 8.53 + 3.90 • HAQ + 0.47 • VAS pain + 4.73 • DAS28 (R2 = 0.28),
DA (%) = 11.27 + 11.87 • HAQ + 0.36 • VAS pain + 1.96 • DAS28 (R2 = 0.44).
Verification of the predicted WPAI values using the data of an additional group has demonstrated the coincidence of the predicted and actual values for presenteeism and TPD. However, the correlation coefficient between the predicted and actual presenteeism indicators was considerably higher (0.68 vs. 0.51). The predicated DA differed considerably from the actual ones.
Conclusion. Multiple regression analysis was used to obtain and verify the prognostic equations for presenteeism, TPD, and DA. The resulting regression equation for calculating presenteeism is characterized by sufficient significance for predicting this indicator in RA patients. HAQ and RA duration (months) are the most significant variables for predicting work ability.