Rheumatoid Arthritis Diagnosis and Management

Diagnostic Laboratory Tests

The American College of Rheumatology recommends ordering rheumatoid factor, anti-citrullinated protein antibodies, C-reactive protein, erythrocyte sedimentation rate, complete blood count with differential, comprehensive metabolic panel, and urinalysis for initial diagnosis of rheumatoid arthritis 1
Anti-CCP antibodies have the highest specificity (90%) with moderate sensitivity (60%) for RA diagnosis and should be ordered in all suspected cases 1
Rheumatoid factor has lower specificity (70%) but similar sensitivity to anti-CCP and remains an important diagnostic marker 1
Seronegative RA accounts for 20-30% of cases, so negative RF does not exclude the diagnosis 1

CRP is preferred over ESR because it is more reliable, not age-dependent, and provides a simple, validated, reproducible test 1, 2
Approximately 40-50% of patients with active RA can have normal acute phase reactants—do not dismiss the diagnosis based solely on normal ESR/CRP 1

Complete blood count with differential should be ordered to assess for cytopenias before starting treatment and calculate neutrophil-to-lymphocyte ratio 1, 2
Comprehensive metabolic panel including liver function tests, renal function, glucose, and uric acid levels should be ordered 1, 2
Urinalysis should be performed as part of standard initial workup 1, 2

Tuberculosis screening with tuberculin skin test or interferon-gamma release assay should be performed regardless of risk factors 2
Hepatitis B surface antigen, surface antibody, and core antibody should be tested 2
Hepatitis C antibody should be tested 2

The American College of Rheumatology recommends 6 validated measures for point-of-care RA disease activity measurement: CDAI, DAS28, PAS, PAS-II, RAPID-3, and SDAI 3
DAS28 incorporates ESR or CRP, tender joint count, swollen joint count, and patient global assessment 1, 4
SDAI combines clinical assessment and CRP 1, 4
CDAI does not require laboratory tests and relies purely on clinical assessment 1, 4

For patients on methotrexate, leflunomide, or sulfasalazine: CBC, liver transaminases, and serum creatinine should be monitored every 2-4 weeks during first 3 months or after dose increases 2
Hydroxychloroquine requires no routine laboratory monitoring after baseline labs 2
NSAIDs require CBC, liver function tests, and renal function tests every 6-12 months 2
Tocilizumab or tofacitinib require lipid profiles at baseline and monitored periodically 2

The primary treatment target is remission, defined as absence of signs or symptoms of inflammatory disease activity, or at minimum low disease activity, which should be attained within 6 months 1
Measure composite disease activity using SDAI or CDAI at initial visit and every 4-6 weeks during active treatment 1
Baseline imaging with bilateral hand, wrist, and foot X-rays is essential for monitoring structural damage progression 1