Performance of a rheumatoid arthritis records-based index of severity.

OBJECTIVE To assess the performance of a rheumatoid arthritis (RA) records-based index of severity (RARBIS) developed by a Delphi panel process in a cohort of patients with RA. METHODS We reviewed the medical records of 120 RA patients from the New England Veteran's Administration (VA) Healthcare System and collected data on markers of RA disease severity. Markers were refined through a Delphi panel process before developing the RARBIS based on chart review. The RARBIS includes 5 subscales on surgery, radiography, extraarticular manifestations, clinical status, and laboratory values. Factors that were regarded by the Delphi panel as highly related to severity of RA were assigned higher points on the index. We assessed the validity of the RARBIS by comparing it to the intensity of the actual RA treatment that these patients received: low, neither biologic nor disease modifying antirheumatic drug (DMARD) use; moderate, therapy with DMARD such as hydroxychloroquine, gold, or sulfasalazine; high, treatment with stronger DMARD such as methotrexate, azathioprine, leflunomide, and cyclosporine; and very high, use of any biologics. RESULTS The RARBIS had a range of 0 to 8. All subscales except extraarticular manifestations were statistically significantly related to intensity of RA treatment (chi-square test p <or= 0.015); the overall index was linearly correlated with intensity of RA treatment (r = 0.35, 95% CI 0.18-0.55). After adjusting for age and sex in a linear regression, the RARBIS was found to be an independent predictor of intensity of treatment (beta for 1-point increase in score = 0.16, p = 0.002). CONCLUSION A medical records-based index of RA severity was developed with attention to face and criterion validity that correlated moderately with RA treatment intensity (construct validity) in a VA population. Further tests of the RARBIS are recommended before it can be used as a tool to adjust for RA disease severity in performing epidemiologic studies on the safety of drugs.