Diagnosis and Management of Rheumatic Fever

Clinical Use of Antistreptolysin O (ASO) Titre

The primary clinical use of ASO titre is for confirming recent Group A Streptococcal (GAS) infection in patients with suspected nonsuppurative complications, such as acute rheumatic fever or acute glomerulonephritis, as recommended by the American Heart Association, and not for diagnosing acute pharyngitis 1
ASO titres begin to rise approximately 1 week after infection and peak 3-6 weeks after infection, with elevated titres persisting for several months after uncomplicated GAS infections, according to the American Heart Association 1
Normal ASO values vary by age, with higher values in school-age children than adults, as noted by the American Academy of Pediatrics 1
The American Academy of Pediatrics suggests that ASO titres reflect past, not present immunologic events, and cannot distinguish between true infection and carrier state, highlighting the need for careful interpretation 1

Age-specific normal ranges must be considered when interpreting ASO titres, as children have higher normal values than adults, as recommended by the American Heart Association 1
Elevated ASO titres can occur in conditions unrelated to post-streptococcal diseases, highlighting the need for careful interpretation in the context of clinical presentation, according to the American Heart Association 1

The American Heart Association suggests ordering both ASO and anti-DNase B tests when possible to increase diagnostic sensitivity for confirming recent GAS infection, with anti-DNase B titres beginning to rise 1-2 weeks and peaking 6-8 weeks after infection 1
Acute rheumatic fever (ARF) diagnosis requires evidence of preceding group A streptococcal infection plus either two major criteria or one major and two minor criteria, as recommended by the American Heart Association, with major criteria including carditis, polyarthritis, chorea, erythema marginatum, and subcutaneous nodules, and minor criteria including polyarthralgia, fever, elevated acute phase reactants, and prolonged PR interval on ECG 2, 3

The 2015 revised Jones criteria for rheumatic fever diagnosis include the following laboratory tests:

Test	Threshold
Erythrocyte sedimentation rate (ESR)	≥60 mm in the first hour for low-risk populations and ≥30 mm/h for moderate/high-risk populations
C-reactive protein (CRP)	≥3.0 mg/dL
Complete blood count	leukocytosis (>10,000 white blood cells/mm³) and anemia may be present
Electrocardiogram (ECG)	prolonged PR interval (minor criterion)

Rheumatic fever presents with a constellation of symptoms including carditis, polyarthritis, chorea, erythema marginatum, and subcutaneous nodules as major manifestations, along with fever, elevated inflammatory markers, and prolonged PR interval as minor manifestations, according to the American Heart Association 3
Clinical findings include new murmurs, tachycardia out of proportion to fever, and precordial pain, which can indicate carditis, as noted by the American Heart Association 3
Subclinical carditis can be detected only by echocardiography, showing pathological regurgitation, and can involve the endocardium, myocardium, and pericardium, as reported by the American Heart Association 3

First-line treatment with Penicillin V orally for 10 days or benzathine penicillin G as a single intramuscular injection is recommended, as stated by the American Heart Association, with secondary prophylaxis with benzathine penicillin G 1.2 million units IM every 3-4 weeks for a minimum of 5 years or until 21 years of age, or 10 years or until 21 years of age for carditis without residual heart disease, and 10 years or until 40 years of age for carditis with residual heart disease 3
Anti-inflammatory therapy for carditis, such as prednisone, is indicated for acute rheumatic carditis, with a typical regimen of 1-2 mg/kg/day (maximum 60 mg/day) for 2-3 weeks, followed by gradual tapering over 2-3 weeks, as recommended by the American Heart Association 3
Echocardiography is crucial for detecting subclinical carditis and monitoring disease progression, as stated by the American College of Cardiology, with medical therapy, including ACE inhibitors or ARBs, beta-blockers, and careful BP management, may be necessary for those with ventricular dysfunction, as noted by the American Heart Association guidelines 4, 5

Mitral stenosis develops over time with repeated episodes of rheumatic fever, according to the American Heart Association guidelines, with aortic regurgitation being more common initially, and aortic stenosis can develop in chronic disease, as stated by the World Heart Federation guidelines 5, 6
Combined mitral stenosis and regurgitation is common in chronic rheumatic heart disease, with aortic valve involvement being the second most commonly affected valve, as reported by the World Heart Federation guidelines 6
The World Heart Federation guidelines stage rheumatic heart disease as follows:
Monitoring with regular echocardiographic assessment is crucial, with frequency depending on disease severity, as reported by the American Heart Association guidelines, with medical therapy, including ACE inhibitors or ARBs, beta-blockers, and careful BP management, may be necessary for those with ventricular dysfunction 5