From the Guidelines
Rheumatoid arthritis diagnosis and monitoring should include laboratory tests such as rheumatoid factor, anti-cyclic citrullinated peptide antibodies, erythrocyte sedimentation rate, and C-reactive protein, as recommended by the 2015 American College of Rheumatology guideline 1. When diagnosing and monitoring rheumatoid arthritis, it is essential to consider the following laboratory tests:
- Rheumatoid factor (RF)
- Anti-cyclic citrullinated peptide (anti-CCP) antibodies
- Erythrocyte sedimentation rate (ESR)
- C-reactive protein (CRP) These tests help assess disease activity, treatment response, and potential medication side effects. According to the European Standing Committee for International Clinical Studies Including Therapeutics (ESCISIT) recommendations 1, patients presenting with arthritis of more than one joint should be referred to a rheumatologist, and laboratory tests such as complete blood count, urinary analysis, transaminases, and antinuclear antibodies should be performed to exclude diseases other than rheumatoid arthritis. Regular monitoring of disease activity, including tender and swollen joint count, patient's and physician's global assessments, ESR, and CRP, is crucial in guiding treatment decisions and assessing medication effectiveness 1. Additionally, the 2015 American College of Rheumatology guideline recommends specific follow-up laboratory monitoring intervals for patients with rheumatoid arthritis receiving disease-modifying antirheumatic drugs (DMARDs) 1. For example, patients on methotrexate should have laboratory tests, such as complete blood count and liver transaminase levels, monitored every 2-4 weeks for the first 3 months, and then every 8-12 weeks 1. By following these guidelines and incorporating laboratory tests into the diagnosis and monitoring of rheumatoid arthritis, healthcare providers can optimize treatment outcomes and improve patient quality of life.
From the Research
Rheumatoid Arthritis Lab Tests
- Rheumatoid arthritis is typically diagnosed through a combination of clinical evaluation and laboratory tests, including rheumatoid factor, anti-cyclic citrullinated peptide antibody, C-reactive protein, and erythrocyte sedimentation rate 2, 3, 4, 5, 6.
- The presence of a rheumatoid factor or anti-citrullinated protein antibody, or elevated C-reactive protein level or erythrocyte sedimentation rate suggests a diagnosis of rheumatoid arthritis 2, 3.
- Initial laboratory evaluation should also include complete blood count with differential and assessment of renal and hepatic function 2.
- Patients taking biologic agents should be tested for hepatitis B, hepatitis C, and tuberculosis 2.
Laboratory Test Limitations
- Although laboratory tests can be helpful in diagnosing and managing rheumatoid arthritis, they have limitations and cannot serve as a gold standard for diagnosis and management in all individual patients with RA 4.
- More than 30% of patients with RA have negative tests for rheumatoid factor or anti-CCP antibodies, and 40% have a normal ESR or CRP 4.
Diagnostic Test Sensitivity and Specificity
- The sensitivity, specificity, and accuracy of rheumatoid factor in the diagnosis of RA were 91.0%, 74.4%, and 87.0%, respectively 6.
- The sensitivity, specificity, and accuracy of anti-CCP antibody in the diagnosis of RA were 88.0%, 90.4%, and 88.1%, respectively 6.
- Combined detection of rheumatoid factor, anti-CCP antibody, C-reactive protein, and erythrocyte sedimentation rate is beneficial when confirming a diagnosis of RA 6.