THE USE OF RHEUMATOID FACTORS IN CLINICAL-PRACTICE

Rheumatoid factor is a commonly requested test in the investigation of joint problems. Although the test has been found to be both sensitive and specific for rheumatoid arthritis in patients attending Rheumatol ogy Clinics, when the test is applied to general hospital or community populations it performs poorly. Thus the setting in which rheumatoid factor tests are requested and awareness of the test's limitations are critical for appropriate use and interpretation of results. We studie d 295 consecutive requests for testing at four centres. The majority w ere performed for the investigation of joint problems but only 6% of t hese were positive, suggesting unselective requesting. Half of the res ults were used to make diagnoses and influence management. However, si gnificant numbers of clinicians felt that the test result had either e xcluded or confirmed a diagnosis of rheumatoid arthritis suggesting th at results were being over-interpreted and that clinical decisions mad e on this basis may have been inappropriate. We conclude that in this setting rheumatoid factor testing is of limited value and generates mi sleading information.