From the Guidelines
Laboratory tests recommended for suspected Rheumatoid Arthritis (RA) include rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (ACPA), as these are predictive of RA diagnosis and prognosis. The evaluation of patients with undifferentiated peripheral inflammatory arthritis should include testing of RF and/or ACPA, as stated in the 2011 study published in the Annals of the Rheumatic Diseases 1.
Key Laboratory Tests
- Rheumatoid factor (RF)
- Anti-cyclic citrullinated peptide antibodies (ACPA)
- Additional autoantibody tests if a connective tissue disease/systemic inflammatory disorder is suspected
The presence of ACPA or RF increases the probability of developing persistent synovitis or a worse radiographic outcome, as noted in the study 1. Although other markers, such as anti-keratin antibodies (AKA) and anti-perinuclear factor, may have diagnostic usefulness, the evidence for their diagnostic or prognostic value is not as strong as that for RF and ACPA.
Clinical Evaluation
Clinical examination is crucial in detecting synovitis, and in doubtful cases, ultrasound, power Doppler, and MRI might be helpful, as recommended in the 2007 EULAR guidelines for the management of early arthritis 1. A complete blood count, urinary analysis, transaminases, and antinuclear antibodies should be included in the laboratory tests to exclude diseases other than rheumatoid arthritis.
Disease Activity Assessment
The number of swollen and tender joints, ESR or CRP, levels of rheumatoid factor and anti-CCP antibodies, and radiographic erosions should be measured to predict persistent and erosive disease, as suggested in the 2007 EULAR guidelines 1. Regular monitoring of disease activity and adverse events should guide decisions on choice and changes in treatment strategies.
From the Research
Lab Tests for Suspected Rheumatoid Arthritis (RA)
The following lab tests are recommended for suspected Rheumatoid Arthritis (RA):
- Rheumatoid Factor (RF) 2
- Anti-cyclic citrullinated peptide (anti-CCP) antibody 3, 4, 2, 5
- Anti-mutated citrullinated vimentin (anti-MCV) antibodies 3, 6
- C-reactive protein (CRP) 4, 2, 5
- Erythrocyte sedimentation rate (ESR) 4, 2
- Anti-carbamylated protein (anti-CarP) antibodies 4
Diagnostic Sensitivity and Specificity
The diagnostic sensitivity and specificity of these lab tests vary:
- Anti-CCP antibody: sensitivity 88.0%, specificity 90.4% 2
- RF: sensitivity 91.0%, specificity 74.4% 2
- Anti-MCV antibodies: sensitivity 63%, specificity 83% 3
- Anti-CarP antibodies: sensitivity 78.2%, specificity 69.1% 4
Combination of Lab Tests
Combining multiple lab tests can improve diagnostic accuracy: