What is the diagnostic approach for acute rheumatic fever?

Diagnostic Approach for Acute Rheumatic Fever

The diagnosis of acute rheumatic fever requires evidence of preceding Group A Streptococcal infection plus fulfillment of the revised Jones criteria, with either two major manifestations or one major and two minor manifestations. 1

Evidence of Preceding Streptococcal Infection

Testing for recent Group A Streptococcal infection is essential and can be documented by:

• Anti-streptococcal antibody tests:

  • Anti-streptolysin O (ASO) titer - begins rising approximately 1 week after infection and peaks between 3-6 weeks 2
  • Anti-DNase B - rises 1-2 weeks after infection and peaks 6-8 weeks post-infection 2
  • Using both ASO and anti-DNase B tests together provides better sensitivity (95.5%) and specificity (88.6%) 2

• Other supporting evidence:

  • Positive throat culture for Group A Streptococcus
  • Positive rapid antigen detection test for Group A Streptococcus

Revised Jones Criteria (2015)

Major Criteria

1. Carditis (clinical or subclinical)

   • Clinical carditis: New murmur, heart failure, pericarditis
   • Subclinical carditis: Detected by echocardiography even without auscultatory findings 1
   • Echocardiography Doppler is essential for documenting valvular regurgitation (mitral or aortic) 2

2. Arthritis

   • In low-risk populations: Polyarthritis only
   • In moderate/high-risk populations: Monoarthritis or polyarthritis
   • Polyarthralgia (in moderate/high-risk populations only) 1

3. Chorea (Sydenham's)

4. Erythema marginatum

5. Subcutaneous nodules

Minor Criteria

1. Fever (≥38.5°C in low-risk, ≥38.0°C in moderate/high-risk populations)

2. Arthralgia (polyarthralgia in low-risk populations only)

3. Elevated acute phase reactants:

   • Erythrocyte sedimentation rate ≥30 mm/h
   • C-reactive protein ≥3.0 mg/dL 2

4. Prolonged PR interval on ECG (after accounting for age variability)

Diagnostic Algorithm

1. Suspect acute rheumatic fever in patients (especially children 5-14 years) presenting with:

   • Fever
   • Joint pain/swelling
   • Cardiac symptoms
   • Chorea
   • Recent history of sore throat

2. Document Group A Streptococcal infection:

   • Obtain ASO and anti-DNase B titers
   • Consider throat culture or rapid antigen test if infection seems recent

3. Assess for Jones criteria:

   • Clinical examination:

     • Complete cardiac examination (auscultation for murmurs)
     • Joint examination (arthritis)
     • Skin examination (erythema marginatum, subcutaneous nodules)
     • Neurological examination (chorea)

   • Laboratory tests:

     • Complete blood count
     • ESR and CRP
     • ECG (for PR interval prolongation)
     • Echocardiography - essential for detecting clinical and subclinical carditis 1, 2

4. Apply revised Jones criteria:

   • Initial ARF: 2 major OR 1 major + 2 minor criteria PLUS evidence of preceding GAS infection
   • Recurrent ARF with established RHD: 2 major OR 1 major + 2 minor OR 3 minor criteria 1

Special Considerations

• Subclinical carditis: Echocardiographic evidence of valvular regurgitation without audible murmur is now considered a major criterion 1

• Risk stratification: Different diagnostic thresholds apply based on population risk:

  • Low-risk populations: Stricter criteria
  • Moderate/high-risk populations: More inclusive criteria (e.g., monoarthritis can qualify) 1

• Recurrent rheumatic fever: In patients with a history of ARF or established RHD, the diagnostic threshold is lower:

  • 2 major OR 1 major + 2 minor OR 3 minor manifestations may be sufficient 1

Common Pitfalls to Avoid

• Misinterpreting ASO titers: Elevated titers reflect past immunologic events, not acute infection 2

• Failing to consider age-specific normal values: ASO titers are normally higher in school-age children than adults 2

• Overlooking subclinical carditis: Patients without audible murmurs may still have echocardiographic evidence of carditis - approximately 1/3 of carditis cases may be detected by echo only 3

• Stopping prophylaxis prematurely: Patients who discontinue prophylaxis are at high risk for recurrence 3

• Confusing with mimics: Conditions like Lyme disease, serum sickness, drug reactions, and post-streptococcal reactive arthritis can present similarly 4

By following this systematic approach and applying the revised Jones criteria appropriately, clinicians can accurately diagnose acute rheumatic fever and initiate appropriate management to prevent long-term cardiac sequelae.