Comparison of estimated medical costs among patients who are defined as having rheumatoid arthritis using three different standards.

Accurate estimation of medical care costs raises a host of challenging issues. We examined whether pure administrative claims data without clinical validation of diagnosis allow reasonable estimation of disease-related costs in rheumatoid arthritis (RA). Three patient groups were examined: patients with clinically confirmed RA (group A, n=338), patients with likely RA (administrative claims data reported the diagnosis of RA and patients were treated with disease modifying antirheumatic drugs, DMARDs; group B, n=303), and patients with possible RA (same as group B but patients had no DMARD treatment; group C, n=685). The payer's perspective was taken for this analysis. Only direct costs were included in the analysis. Cost data and data for several covariates were obtained from a major German statutory health insurance plan, the AOK Niedersachsen. A patient-per-patient microcosting approach was performed. A repeated measures, fixed effects model was applied to examine differences between the three study groups. Mean+/-SEM annual RA-related direct costs were euro 2,017+/-183 per patient-year in group A, euro 1,763+/-192 in group B, and euro 805+/-58 in group C. Outpatient (inpatient) costs were euro 1,636 (328) in group A, euro 1344 (340) in group B, and euro 546 (136) in group C. DMARD costs were by far the single most important cost driver in groups A and B. The difference in total RA-related direct cost between groups A and B was not significant whereas the differences between groups A and C (group B and C respectively), were significant. Pure administrative claims data allowed for an accurate estimate of disease-related costs in RA patients that received DMARD therapy. However, the high number of patients for whom administrative claims data listed the diagnosis RA, but no DMARD treatment was given poses a challenge for further research.