Methodological issues when measuring paid productivity loss in patients with arthritis using biologic therapies: an overview of the literature.

Many patients with RA, AS and PsA experience restrictions in participating in the labour force. This reduces quality of life but also affects social insertion and economic autonomy of a patient. During the past decade, treatment strategies have been intensified and, additionally, a number of biologic therapies have been introduced for the treatment of these diseases. Treatment with biologic therapies has proved to be clinically effective and retard radiographic damage. Although less frequently investigated, a number of studies also determined the impact of biologic therapy on employment. However, the results in these studies are conflicting, which may partly be explained by the variation in methods used to assess the association between biologic therapy and employment/productivity loss. The aim of this overview is to critically appraise the different methodological approaches used in studies that evaluated the effect of biologic therapies on employment/productivity loss outcomes in inflammatory arthritis. The specific aims are to compare and discuss: (i) differences in population characteristics and study design including the use of a control group; and (ii) differences in methods used to assess and quantify productivity loss.