Value of laboratory tests in early prediction of rheumatoid arthritis

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Abstract
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.