Investigations for rheumatoid arthritis

It can be difficult to definitively diagnose rheumatoid arthritis (RA) in the early phase of an inflammatory polyarthritis—see Acute polyarthritis in adults for an approach to the assessment.

Specific investigation findings can support a suspected diagnosis of RA. These include positive autoantibodies and evidence of systemic inflammation (eg elevated erythrocyte sedimentation rate [ESR] and serum C-reactive protein [CRP] concentration). See Clinical features and investigation findings suggestive of early rheumatoid arthritis for investigation findings suggestive of early RA.

Detection of rheumatoid factor (RF) and autoantibodies to cyclic citrullinated peptides (anti-CCP antibodies) can help resolve diagnostic uncertainty in people with suspected RA; see Utility of autoantibodies for rheumatological diseases for more detail about these investigations. While RF is present in about 70% of people with established RA, it is detected less frequently in early diseaseIngegnoli, 2013Myasoedova, 2010. Anti-CCP antibodies may be present before symptoms develop and have a 96% specificity for RA; however, up to 30% of people with RA never develop positive RF or anti-CCP antibodies and are said to have seronegative disease.

Note: People who are symptomatic and have positive rheumatoid factor or anti-CCP antibodies should be referred to a specialist as soon as possible because early joint damage is likely to occur.

Rheumatologists often have fast-track triage systems for people with suspected RA and strongly encourage direct contact by general practitioners to expedite referral or to obtain advice on treatment. For symptomatic people who are positive for RF or anti-CCP antibodies, prompt referral to a specialist is required because early joint damage is likely to occur. For people who are seronegative for RF or anti-CCP antibodies, but have persistently swollen joints, review by a specialist ideally should occur within 6 weeks of symptom onset.