Review of health economics modelling in rheumatoid arthritis.

As the cost of drug treatment for rheumatoid arthritis (RA) constitutes only a small proportion of total costs of the disease to individuals and society, therapeutic interventions have the potential for significant economic benefit. To take advantage of this potential, clinicians need to gain a global, long-term perspective on patient care. Economic evaluations of RA therapies are critically important in influencing decisions regarding the role of costly, but highly effective new therapies, particularly in settings where there are financial constraints on healthcare provisions. Such evaluations, therefore, need to be methodologically similar with valid results to enhance their value to clinicians and policy decision-makers. This requires the use of appropriate elements in the numerator (i.e. total number of dollars spent on healthcare as a result of the intervention) and the denominator (net health effectiveness) components of the cost-effectiveness equation. Other important design factors also need to be managed properly to ensure validity of the evaluation. In this regard, the guidelines proposed by the Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT) Task Force represent a useful approach to help create common standards for economic evaluations in RA. Recently, the development of a number of decision analysis models in RA has helped predict the likely cost-effectiveness of new interventions such as the anti-tumour necrosis factor (TNF)-alpha agents, etanercept and infliximab, both of which have been found to be cost-effective relative to other disease-modifying anti-rheumatic drugs (DMARDs) using short-term efficacy endpoints. In comparisons of these two agents in patients with DMARD-resistant RA, etanercept has been shown to be more cost-effective than the combination of methotrexate and infliximab, administered in various dosages, over a period of 1 year using American College of Rheumatology (ACR) response rates as the primary efficacy measure. However, the criteria for determining clinical efficacy is paramount and other studies that use radiographic progression as a measure of clinical effectiveness show no difference between etanercept and infliximab in clinical efficacy. Important issues that need to be considered in developing economic models in RA include consideration of the connection between the prevention of radiographic progression and downstream economic consequences, and the need to employ lifetime models wherever possible because a long time period is necessary to determine the true cost-effectiveness of agents that modify radiographic progression of RA, such as etanercept, infliximab, and adalimumab. In doing so, it is hoped that such studies will provide optimal information to facilitate important decisions on resource allocation.