Evaluative laboratory testing practices of United States rheumatologists

Several laboratory tests can be used to monitor disease activity in patients with rheumatic diseases. We sought to learn how rheumatologists use evaluative laboratory tests in the care of patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis.

We surveyed United States rheumatologists by mailed questionnaire. Of the 976 rheumatologists who received the questionnaire, 575 responded, for a response rate of 59%.

Eighty-six percent of the respondents reported using either the erythrocyte sedimentation rate (ESR) or C-reactive protein level to monitor patients with RA, 92% used either the anti-DNA antibody level or complement C3 level to monitor patients with SLE, and 95% used either the ESR or ANCA levels to monitor patients with ANCA-associated vasculitis. The frequency of testing was distributed over a broad range, but testing was common. Testing on 50% of the visits or more was reported by 52% of respondents for RA, 59% of respondents for SLE, and 64% of respondents for ANCA-associated vasculitis. Between 7% and 11% of respondents reported testing patients on every visit, regardless of clinical disease activity. The majority of respondents reported not altering the treatment of clinically stable patients based on these test results.

Evaluative laboratory testing is common, and is rarely used as an independent guide for treatment.