From the Guidelines
Rheumatoid labs are indicated when evaluating patients with suspected rheumatoid arthritis (RA) or monitoring disease activity in those with established RA, particularly in patients presenting with persistent joint pain, swelling, morning stiffness lasting more than 30 minutes, or symmetric involvement of small joints, as recommended by the 2017 EULAR guidelines 1. The primary rheumatoid labs include rheumatoid factor (RF), anti-cyclic citrullinated peptide antibodies (anti-CCP), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).
- RF and anti-CCP are specific markers for RA, with anti-CCP being more specific (95-98%) than RF (80%) 1.
- ESR and CRP are non-specific inflammatory markers that help assess disease activity and monitor treatment response. Additional labs often included are:
- Complete blood count to check for anemia of chronic disease
- Comprehensive metabolic panel to evaluate organ function before starting medications
- Baseline hepatitis serologies since many RA medications can affect liver function Early testing is crucial as prompt diagnosis and treatment within the first 3-6 months of symptom onset can prevent joint damage and improve long-term outcomes, as supported by the 2016 American College of Rheumatology guideline for the treatment of rheumatoid arthritis 1. The 2009 NICE guidance also recommends offering to test for rheumatoid factor in people with suspected rheumatoid arthritis who have synovitis 1. However, the most recent and highest quality study, the 2017 EULAR guidelines, should be prioritized in clinical decision-making 1.
From the Research
Indications for Rheumatoid Labs
Rheumatoid labs are indicated for the diagnosis and management of rheumatoid arthritis (RA). The following are some of the key indications:
- To explore the value of rheumatoid factor (RF), anti-cyclic citrullinated peptide (CCP) antibody, C-reactive protein (CRP), and the erythrocyte sedimentation rate (ESR) in the diagnosis of RA 2
- To assess patients with RA and monitor their response to treatment 3
- To diagnose RA in patients with inflammatory arthritis, particularly those with a positive rheumatoid factor and/or anti-citrullinated protein antibody, elevated CRP level, or elevated ESR 4
- To evaluate the sensitivity and specificity of anti-carbamylated protein (anti-CarP) antibodies in individuals with RA and their relationship with inflammatory markers such as CRP and ESR 5
- To predict the development of RA and an erosive phenotype, particularly in patients with a synergic effect of RF and ACPA 6
Laboratory Tests for Rheumatoid Arthritis
The following laboratory tests are commonly used to diagnose and manage RA:
- Rheumatoid factor (RF)
- Anti-cyclic citrullinated peptide (CCP) antibody
- C-reactive protein (CRP)
- Erythrocyte sedimentation rate (ESR)
- Anti-carbamylated protein (anti-CarP) antibodies
Clinical Applications of Rheumatoid Labs
Rheumatoid labs have several clinical applications, including: