How to diagnose rheumatic fever in a general outpatient department (OPD)?

Diagnosing Rheumatic Fever in General OPD

Use the revised 2015 Jones Criteria with mandatory echocardiography for all suspected cases, requiring documented streptococcal infection plus either 2 major criteria OR 1 major plus 2 minor criteria, with different thresholds for high-risk versus low-risk populations. 1, 2

Step 1: Document Preceding Streptococcal Infection (Mandatory)

You cannot diagnose acute rheumatic fever without this evidence (except rare cases of isolated chorea or indolent carditis): 2, 3

• Throat culture or rapid strep test (if patient presents acutely) 4
• Anti-streptolysin O (ASO) titers - elevated or rising 3, 5
• Anti-DNase B antibodies 4

Step 2: Determine Population Risk Status

This fundamentally changes your diagnostic thresholds: 1, 2

Low-risk populations: ARF incidence ≤2 per 100,000 school-aged children 1

Moderate-to-high-risk populations: Higher incidence areas (most developing countries, indigenous populations) 1, 6

Step 3: Identify Major Criteria (Population-Specific)

Carditis (All Populations)

Critical: Order echocardiography with Doppler on EVERY suspected case, regardless of auscultation findings - cardiac auscultation alone has very low sensitivity and will miss cases. 2, 7

Echocardiographic criteria for pathological mitral regurgitation: 1, 8

• Jet visible in 2 planes
• Jet length >1 cm
• Holosystolic
• Peak velocity >2.5 m/s

Echocardiographic criteria for pathological aortic regurgitation: 1, 8

• Jet visible in 2 planes
• Holodiastolic
• Peak velocity >2.5 m/s

Arthritis (Population-Dependent)

Low-risk populations: Only polyarthritis qualifies 1

Moderate-to-high-risk populations: 1, 8

• Monoarthritis qualifies as major criterion
• Polyarthritis qualifies
• Polyarthralgia (after excluding other causes) qualifies as major criterion

The widespread availability of NSAIDs means you must take detailed history - many patients will have taken antipyretics before presentation, masking the migratory pattern. 1

Other Major Criteria (All Populations)

• Chorea (Sydenham's) 1, 3
• Erythema marginatum 1, 8
• Subcutaneous nodules 1, 8

Step 4: Identify Minor Criteria (Population-Specific)

Low-Risk Populations: 1

• Polyarthralgia
• Fever ≥38.5°C
• ESR ≥60 mm/h and/or CRP ≥3.0 mg/dL
• Prolonged PR interval on ECG (unless carditis is major criterion)

Moderate-to-High-Risk Populations: 1

• Monoarthralgia (lower threshold)
• Fever ≥38.0°C (lower threshold)
• ESR ≥30 mm/h and/or CRP ≥3.0 mg/dL (lower threshold)
• Prolonged PR interval on ECG (unless carditis is major criterion)

Important caveat: CRP must be greater than upper limit of normal for your laboratory. Normal ESR and CRP essentially rule out ARF except in isolated chorea. 1

Step 5: Apply Diagnostic Algorithm

For initial ARF: 2 major manifestations OR 1 major + 2 minor manifestations 1

For recurrent ARF (in patients with prior RF/RHD history): 2 major OR 1 major + 2 minor OR 3 minor manifestations may suffice 1, 8

Critical rule: Joint manifestations can only count in either major OR minor category, never both. 1

Key Differential Diagnoses to Exclude

When evaluating suspected carditis on echo: 1

• Physiological mitral regurgitation - use continuous-wave Doppler; signals with peak velocity <3.0 m/s and non-holosystolic are more likely physiological
• Mitral valve prolapse/Barlow syndrome - in RF, only the coapting leaflet tip prolapses without billowing of the body
• Infective endocarditis - can mimic rheumatic carditis if no obvious vegetation
• Congenital valve abnormalities - bicuspid aortic valve, cleft mitral valve

When evaluating arthritis: 3

• Post-streptococcal reactive arthritis
• Lyme disease
• Serum sickness
• Drug reactions

Common Pitfalls to Avoid

1. Never rely on auscultation alone - you will miss subclinical carditis, which is now a major criterion. 2, 7

2. Measure blood pressure during echocardiography - three of four Doppler criteria are influenced by systemic blood pressure; document BP for proper interpretation and serial comparisons. 1

3. Don't diagnose without documented streptococcal infection - except in rare cases of isolated chorea or indolent carditis. 2

4. Account for NSAID use - patients often self-medicate before presentation, masking fever and arthritis patterns. 1

5. Use peak ESR values - ESR evolves during the course of ARF. 1

When Diagnosis is Uncertain

If clinical suspicion remains high but criteria not fully met: 1, 4

• Offer 12 months of secondary prophylaxis (benzathine penicillin G 1.2 million units IM every 4 weeks)
• Reevaluate after 12 months with detailed history, physical exam, and repeat echocardiogram
• If patient has recurrent symptoms on prophylaxis but lacks serological evidence of streptococcal infection and lacks echocardiographic valvulitis, discontinue prophylaxis - symptoms likely not RF-related