What blood work should I consider for unilateral hand swelling/pain to rule out (r/o) a rheumatologic cause?

Blood Work for Unilateral Hand Swelling/Pain to Rule Out Rheumatologic Causes

For unilateral hand swelling and pain, the essential blood work to rule out rheumatologic causes includes ESR, CRP, RF, and anti-CCP antibodies, with additional autoantibody tests when specific connective tissue disorders are suspected. 1, 2

First-Line Laboratory Tests

• Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP)

  • Should be performed at baseline for diagnosis and prognosis of inflammatory arthritis 1, 2
  • ESR has diagnostic value for rheumatoid arthritis but limited prognostic value 2
  • CRP is more useful for acute inflammatory conditions, while ESR is better for monitoring chronic inflammation 3

• Rheumatoid Factor (RF)

  • Sensitivity: 69-84%, Specificity: 78-85% 2
  • Higher sensitivity but lower specificity than anti-CCP 2
  • Positive RF increases probability of developing persistent synovitis 1

• Anti-Citrullinated Protein Antibodies (ACPA)/Anti-CCP

  • Sensitivity: 67-78.5%, Specificity: 95-98% 2
  • Highest specificity for rheumatoid arthritis 2, 4
  • Presence increases probability of developing persistent synovitis or worse radiographic outcome 1

• Complete Blood Count (CBC)

  • Essential baseline investigation to exclude other causes of joint symptoms 2

• Liver Function Tests

  • Important baseline before potential DMARD therapy 2
  • Helps exclude other diseases that may cause joint symptoms 2

Additional Tests Based on Clinical Suspicion

• Antinuclear Antibody (ANA)

  • Consider if systemic lupus erythematosus or other connective tissue disorders are suspected 2, 5
  • Not specific for RA, more relevant for other autoimmune conditions 2

• HLA-B27

  • Not routinely recommended but helpful if spondyloarthropathy is suspected 1, 2
  • Particularly useful in RF and ACPA-negative patients with suspected spondyloarthritis 1

• Anti-Mutated Citrullinated Vimentin (anti-MCV)

  • Consider in RF and anti-CCP2 seronegative patients 4
  • Similar diagnostic performance to anti-CCP2 but with a somewhat different diagnostic spectrum 4

• Thyroid Function Tests

  • Can help rule out thyroid disorders that can present with joint pain 2

Imaging Considerations

While not blood work, these are important complementary tests:

• X-rays of affected joints

  • Should be performed at baseline 1
  • X-rays of hands, wrists, and feet should be considered as presence of erosions predicts development of RA 1, 2

• MRI of hands and wrists

  • Not recommended for routine use but could be considered when RA is suspected 1, 2
  • Bone edema is an independent predictor of future development of RA 1

Interpretation Considerations

• Negative RF and anti-CCP do not exclude RA diagnosis 2, 6
• ESR and CRP can be influenced by non-inflammatory factors such as age, gender, anemia 2
• Discordance between ESR and CRP occurs in about 28% of cases 2
• Elevated inflammatory markers can occur in various conditions including infections and malignancies 2

Common Pitfalls to Avoid

• Overreliance on a single test can lead to misdiagnosis 2
• Inadequate consideration of other diagnoses with similar presentations (psoriatic arthritis, gout, hemochromatosis) 1
• Delayed referral to a rheumatologist (should be within 6 weeks of symptom onset) 2
• Failing to repeat tests when clinically indicated, especially if symptoms persist 1

Remember that unilateral hand involvement is less typical for rheumatoid arthritis, which tends to be bilateral and symmetric. Consider other diagnoses such as psoriatic arthritis (which may target DIPJs or affect just one ray), gout (which may superimpose on pre-existing hand osteoarthritis), or hemochromatosis (mainly targeting MCPJs, wrists) 1.