From the Guidelines
Rheumatoid Arthritis (RA) laboratory tests include anti-cyclic citrullinated peptide antibody (anti-CCP), rheumatoid factor (RF), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).
Key Laboratory Tests
- Anti-CCP: has a high specificity (.96,95% CI 0.94–0.97) and a pooled diagnostic odds ratio (DOR) of 43.05 (95% CI 32.00–57.93) for diagnosing RA 1
- Rheumatoid Factor (RF): should be tested in people with suspected RA who have synovitis, as it is predictive of RA diagnosis and prognosis 1
- ESR and CRP: are used to measure disease activity and are part of the DAS28 and SDAI measures 1
Additional Tests
- Anti-keratin antibodies (AKA) and anti-perinuclear factor: may have diagnostic usefulness, but the evidence is limited 1
- Other autoantibody tests: may be considered if non-RA systemic inflammatory disorders are suspected 1 It is essential to note that negative tests do not exclude progression to RA, and a combination of clinical evaluation and laboratory tests is necessary for accurate diagnosis and management of RA 1.
From the Research
Laboratory Tests for Rheumatoid Arthritis (RA)
The following laboratory tests are used to diagnose and manage RA:
- Rheumatoid factor (RF) test 2, 3, 4, 5, 6
- Anti-cyclic citrullinated peptide (anti-CCP) antibodies test 2, 3, 4, 5, 6
- Erythrocyte sedimentation rate (ESR) test 2, 3
- C-reactive protein (CRP) test 2, 3
- Matrix metalloproteinase 3 (MMP-3) test 4
- Anti-agalactosyl IgG antibodies (CARF) test 4
- IgG-RF test 4
- 14-3-3η protein test 6
- Connective tissue growth factor (CTGF) test 6
- Antibodies against PAD4 test 6
- Antibodies against BRAF test 6
- Anti-acetylated and anti-carbamylated protein antibodies test 6
Limitations of Laboratory Tests
While laboratory tests can be helpful in diagnosing and managing RA, they have limitations:
- Not all patients with RA test positive for RF or anti-CCP antibodies 2, 3
- Some patients with RA may have a normal ESR or CRP 2, 3
- False-positive results can occur in patients without RA 3, 4
- False-negative results can occur in patients with RA 3, 4
Multiple Biomarker Approach
A multiple biomarker approach, which involves measuring a set of biomarkers simultaneously, may improve the diagnosis and treatment of RA 6. However, more research is needed to validate this approach and make it applicable in clinical practice.