Criteria for TNF-Targeted Therapy in Rheumatoid Arthritis

Tumour necrosis factor (TNF) antagonists or blocking agents represent a major advance in the treatment of rheumatoid arthritis (RA), but their use raises economic concerns because of the high drug cost. Population-based patient registers with clinical data allow the estimation of the proportion of patients with RA who are eligible for TNF antagonist therapy according to recent consensus statements on TNF-targeted therapy.

Data were derived from a representative county-based (500 000 population) register of patients with RA. Of 894 patients aged between 18 and 70 years, 636 (71%) [females 80%, mean (SD) age 53.6 (12.2) years and mean (SD) disease duration 12.2 (9.3) years] had a clinical and radiographic examination. The eligibility for TNF-targeted therapy was estimated from the following criteria: (i) previous or current therapy with at least one disease-modifying antirheumatic agent (DMARD); and (ii) active disease. Disease activity criteria were set to 28-swollen joint count (28-SJC) ≥6, 28-tender joint count ≥6, and erythrocyte sedimentation rate (ESR) ≥28 mm/hour or C-reactive protein (CRP) ≥20 mg/L. Sensitivity analyses were performed varying some of these disease activity parameters.

Of the 636 patients, as many as 526 (83%) had previously or were currently using DMARDs and 98 (15%) fulfilled both the DMARD and activity criteria, thus being the maximum number of patients considered for TNF-targeted therapy. If the most stringent criteria were used (ever DMARD, 28-SJC ≥12 and ESR ≥50 mm/hour or CRP ≥40 mg/L) only 15 of the 626 (2%) would be candidates for TNF-targeted therapy. In a population of 1 million, assuming a prevalence of 2000 patients with RA under the age of 70 years, the number of candidates for TNF-targeted therapy would be 40 to 300, depending on the disease activity criteria. Stringent ESR and CRP criteria would lead to a major reduction in the number of eligible patients. These utilisation data imply annual drug costs in the range of $US480 000 to $US3 600 000 for TNF antagonists for RA per 1 million population. Further economic evaluations are needed to determine for which groups such treatment is warranted from a health economics perspective.