Rheumatology Diagnostic Tests

Core Laboratory Tests

• A comprehensive rheumatology workup should include acute phase reactants, autoantibody testing, and appropriate imaging studies to accurately diagnose and monitor rheumatic diseases, as recommended by the American College of Rheumatology 1, 2
• Complete Blood Count (CBC) with differential is essential for detecting cytopenia, anemia, and neutropenia which can be present in various rheumatic diseases, according to the European League Against Rheumatism 2
• C-reactive protein (CRP) is preferred over ESR as it's more reliable, not age-dependent, and correlates more closely with clinical and radiographic parameters of inflammation, as stated by the American College of Rheumatology 1
• Erythrocyte sedimentation rate (ESR) is useful for assessing inflammation in rheumatoid arthritis, polymyalgia rheumatica, and temporal arteritis, as recommended by the European League Against Rheumatism 2
• Anti-citrullinated protein antibodies (ACPA) have high specificity for RA diagnosis and prognosis; negative tests don't exclude progression to RA, according to the American College of Rheumatology 2
• Antinuclear antibodies (ANA) are a screening test for systemic lupus erythematosus and other connective tissue diseases, as recommended by the European League Against Rheumatism 2, 3
• Biochemistry panel, including liver function tests, glucose, urate, and renal function, is useful for monitoring rheumatic diseases, as stated by the American College of Rheumatology 2, 3
• Complement levels (C3, C4) are useful for monitoring SLE activity, according to the European League Against Rheumatism 2
• Immunoglobulins may be elevated in certain inflammatory conditions, as recommended by the American College of Rheumatology 2

Imaging Studies

• X-rays of affected joints should be performed at baseline, particularly hands, wrists, and feet to detect erosions which predict RA development and disease persistence, as recommended by the European League Against Rheumatism 2
• Musculoskeletal ultrasound is valuable for detecting early inflammatory changes in joints, tendons, and bursae; particularly useful for shoulder, elbow, wrist, and hand examinations, according to the American College of Rheumatology 4, 5

Disease-Specific Testing

• Genetic testing using next-generation sequencing (NGS) platforms for CAPS, TRAPS, MKD, and DIRA is recommended for suspected autoinflammatory diseases, as stated by the European League Against Rheumatism 6
• Mevalonic acid in urine is useful for suspected MKD, according to the European League Against Rheumatism 6
• Abdominal ultrasound or CT scan can confirm splenomegaly in suspected Felty's syndrome, as recommended by the American College of Rheumatology 3

Important Considerations

• Repeat laboratory tests when clinically relevant to monitor disease activity and treatment response, as recommended by the European League Against Rheumatism 2
• For undifferentiated peripheral inflammatory arthritis, X-rays of hands, wrists, and feet should be repeated within 1 year to assess for development of erosions, according to the European League Against Rheumatism 2
• Failure to repeat testing can lead to misinterpretation of disease activity; serial testing is often necessary, as stated by the American College of Rheumatology 2