What initial blood work is recommended for a patient with hand pain and a family history of Rheumatoid Arthritis (RA)?

Initial Blood Work for a Patient with Hand Pain and Family History of Rheumatoid Arthritis

For a patient with hand pain and family history of rheumatoid arthritis, the initial blood work should include ESR, CRP, RF, and ACPA (anti-citrullinated protein antibody) testing, along with complete blood count, liver function tests, and renal function assessment. 1

Core Laboratory Tests

• Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP): These acute phase reactants should be performed at baseline for both diagnostic and prognostic purposes in patients with suspected inflammatory arthritis 1
• Rheumatoid Factor (RF): Essential for evaluation as it is predictive of RA diagnosis and prognosis 1
• Anti-Citrullinated Protein Antibodies (ACPA): Should be tested alongside RF as it increases diagnostic certainty for RA and provides prognostic information 1
• Complete Blood Count: Important for baseline assessment and to rule out other conditions 2
• Liver and Renal Function Tests: Essential for baseline assessment before potential treatment initiation 2

Diagnostic Value of Autoantibody Testing

The presence of RF and/or ACPA significantly increases the probability of developing RA, though negative tests do not exclude progression to RA 1. The diagnostic value is enhanced when these tests are considered together:

• RF and ACPA have strong predictive value for RA diagnosis 1
• The presence of these antibodies also correlates with increased probability of developing persistent synovitis and worse radiographic outcomes 1
• It's important to note that more than 30% of patients with RA may have negative tests for RF or ACPA 3

Additional Considerations

• Additional autoantibody tests: If non-RA systemic inflammatory disorders are suspected, additional autoantibody testing should be considered 1
• Imaging: While not a blood test, plain radiographs of hands and wrists should be performed at baseline as they provide important complementary information 1
• Monitoring: These laboratory tests should be repeated when clinically relevant to assess disease activity and treatment response 1

Common Pitfalls to Avoid

• Overreliance on laboratory tests: More than 30-40% of patients with RA may have negative RF or ACPA tests or normal ESR/CRP values 3
• Neglecting clinical assessment: Laboratory tests should complement, not replace, careful clinical examination 1
• Incomplete testing: Failing to order both RF and ACPA reduces diagnostic sensitivity 1
• Misinterpreting normal results: Normal inflammatory markers do not exclude the diagnosis of RA 3

Algorithm for Laboratory Assessment

1. Order core tests: ESR, CRP, RF, ACPA, CBC, liver and renal function tests 1, 2
2. If clinical suspicion is high despite negative initial tests, consider:
   • Repeating tests in 3-6 months if symptoms persist 1
   • Additional autoantibody testing if other systemic disorders are suspected 1
3. Combine laboratory findings with clinical assessment and imaging results for comprehensive evaluation 1

Remember that early diagnosis allows for earlier treatment with disease-modifying agents, potentially preventing joint damage and improving long-term outcomes 2.