What are the diagnostic criteria and treatment options for rheumatic fever?

Diagnosis of Rheumatic Fever

The diagnosis of acute rheumatic fever requires documented evidence of preceding Group A Streptococcal infection plus either 2 major manifestations OR 1 major plus 2 minor manifestations from the revised 2015 Jones Criteria, with different thresholds for low-risk versus moderate-to-high-risk populations. 1, 2

Risk Stratification

Before applying diagnostic criteria, you must first classify the patient's population risk:

• Low-risk populations: ARF incidence ≤2 per 100,000 school-aged children or rheumatic heart disease prevalence ≤1 per 1000 population 1
• Moderate-to-high-risk populations: All other populations, including most developing countries 1, 3

This distinction is critical because the diagnostic thresholds differ substantially between these groups 1, 2.

Major Criteria (Population-Specific)

For Low-Risk Populations:

• Carditis (clinical and/or subclinical detected by echocardiography) 1, 2
• Polyarthritis only (not monoarthritis) 1
• Chorea 1
• Erythema marginatum 1
• Subcutaneous nodules 1

For Moderate-to-High-Risk Populations:

• Carditis (clinical and/or subclinical) 1, 2
• Monoarthritis OR polyarthritis 1, 3
• Polyarthralgia (after excluding other causes) 1, 4
• Chorea 1
• Erythema marginatum 1
• Subcutaneous nodules 1

Critical caveat: Joint manifestations can only be counted in either the major OR minor category, never both in the same patient 1.

Minor Criteria (Population-Specific)

For Low-Risk Populations:

• Polyarthralgia 1
• Fever ≥38.5°C 1, 2
• ESR ≥60 mm/h and/or CRP ≥3.0 mg/dL 1
• Prolonged PR interval (age-adjusted, unless carditis is already a major criterion) 1

For Moderate-to-High-Risk Populations:

• Monoarthralgia 1, 4
• Fever ≥38°C 1, 2
• ESR ≥30 mm/h and/or CRP ≥3.0 mg/dL 1, 4
• Prolonged PR interval (age-adjusted, unless carditis is already a major criterion) 1

Essential Diagnostic Algorithm

Step 1: Document Preceding Streptococcal Infection

You cannot diagnose acute rheumatic fever without documented evidence of Group A Streptococcal infection, except in rare cases of isolated chorea or indolent carditis 2, 5. Evidence includes:

• Positive throat culture or rapid antigen test 6
• Elevated or rising streptococcal antibody titers (ASO, anti-DNase B) 6

Step 2: Perform Echocardiography in ALL Suspected Cases

The American Heart Association mandates standard echocardiography with Doppler in all suspected cases, regardless of auscultation findings 2. This is non-negotiable because:

• Cardiac auscultation alone has very low sensitivity and should never be relied upon as the sole method for excluding cardiac involvement 2
• Subclinical carditis (echocardiographic valvulitis without audible murmur) is now a major criterion and significantly impacts diagnosis 1, 2

Echocardiographic criteria for pathological regurgitation:

• Mitral regurgitation: Jet visible in 2 planes, >1 cm length, holosystolic, peak velocity >2.5 m/s 1, 7
• Aortic regurgitation: Jet visible in 2 planes, holodiastolic, peak velocity >2.5 m/s 1, 7

Step 3: Obtain ECG

Check for prolonged PR interval (age-adjusted), which serves as a minor criterion 2.

Step 4: Apply Jones Criteria Based on Risk Population

For initial ARF diagnosis:

• 2 major manifestations, OR
• 1 major + 2 minor manifestations 1, 2

For recurrent ARF (in patients with prior RF or established rheumatic heart disease):

• 2 major manifestations, OR
• 1 major + 2 minor manifestations, OR
• 3 minor manifestations 1, 2, 7

Critical Pitfalls to Avoid

Subclinical Carditis vs. Physiological Regurgitation

Distinguishing pathological from physiological mitral regurgitation is essential 1, 4:

• Physiological regurgitation: Signals not holosystolic, peak velocity <3.0 m/s 1
• Pathological regurgitation: Must meet strict echocardiographic criteria above 1, 7

Differential Diagnoses That Mimic ARF

You must actively exclude 1, 5:

• Post-streptococcal reactive arthritis (arthritis without carditis, often more severe joint involvement) 2, 5
• Endocarditis (look for vegetations on echo) 1, 7
• Congenital valve abnormalities (bicuspid aortic valve, mitral valve prolapse with myxomatous changes) 1
• Lyme disease, serum sickness, drug reactions 5

Monoarthritis in High-Risk Populations

In moderate-to-high-risk populations, aseptic monoarthritis can be a major criterion, but you must rigorously exclude septic arthritis, trauma, and other causes before attributing it to ARF 1, 4.

"Possible" Rheumatic Fever

When diagnostic uncertainty exists but clinical suspicion remains high, treat as ARF with secondary prophylaxis for 12 months, then reassess 2, 4. This includes:

• Detailed clinical history and physical examination 2
• Repeat echocardiogram at 12 months 2
• Decision to continue or discontinue prophylaxis based on findings 4

This approach prevents the devastating consequences of missed diagnosis (chronic rheumatic heart disease, valve surgery, premature death) while minimizing overdiagnosis 4, 8.