Value of laboratory tests in early prediction of rheumatoid arthritis

OBJECTIVE: To determine which laboratory test or tests at presentation best predicted a diagnosis of rheumatoid arthritis (RA) 2 years later. METHODS: Two hundred seventy patients with early arthritis seen in 7 hospitals underwent comprehensive evaluations at 6-month intervals for 2 years, when the diagnosis of RA was assessed by 5 rheumatologists. The sensitivity and specificity of each test at the first visit for discriminating between RA (38%, n = 98) and non-RA patients were determined. Optimal cutoffs for continuous tests were derived from receiver operating characteristic curves. Sensitivity and specificity of test combinations selected by multiple logistic regression were determined. RESULTS: IgM rheumatoid factor (RF) by enzyme-linked immunosorbent assay, IgG-antikeratin antibody (AKA), and latex test had the strongest associations with RA. These 3 tests formed the most powerful combination for distinguishing RA from non-RA. CONCLUSION: IgM-RF, IgG-AKA, and the latex test are the best laboratory tests for discriminating between patients with and without RA. Combining these tests slightly improves diagnostic value.