Background The past decades have seen rapid advances in the treatment of rheumatoid arthritis (RA). In particular, the introduction of biologic and targeted synthetic disease-modifying antirheumatic drugs have improved clinical outcomes and reconfigured traditional RA cost compositions.

Objectives To map the existing evidence concerning cost of illness of RA, as the treatment pathway evolves in the biologic era, and examine how costs have been measured and estimated, in order to assemble and appropriately interpret available data.

Methods Systematic review of studies that estimated the costs of patients with RA. Multiple electronic databases were searched to identify studies published between 2000 and 2019. The reported total costs and cost components were evaluated according to the study and population characteristics. The Cochran-Armitage test was used to determine statistically significant trends in increasing or decreasing proportions over time.

Results Overall, 72 studies were included. Drug costs compromised the main component (up to 87%) of direct costs with an increasing trajectory over time, although not statistically significant. The proportion of costs for hospitalisation showed a statistically significant decrease chronologically (p=0.044). Indirect costs, primarily associated with absenteeism and work disability accounted for 39% to 86% of total costs. The reported indirect costs are highly sensitive to the approach to estimation.

Conclusions A decreasing trend in inpatient costs chronologically suggested a cost shift in other components of direct costs. Indirect costs still contributed a considerable proportion of total costs, with work disability being the main cost component. Economic analyses that do not incorporate or appropriately measure indirect costs will underestimate the full economic impact of RA.