In an adult with acute streptococcal pharyngitis, what is the risk of developing acute rheumatic fever and what is the recommended treatment and prophylaxis?

Rheumatic Fever Risk in Adults with Streptococcal Pharyngitis

The risk of acute rheumatic fever in adults with streptococcal pharyngitis is extremely low—approaching zero—even when the infection goes undiagnosed and untreated, which fundamentally changes the diagnostic and treatment approach compared to children. 1

Epidemiology of Risk

• Adults account for only 5–10% of all Group A streptococcal pharyngitis cases, compared to 20–30% in children aged 5–15 years. 1
• The risk of a first attack of acute rheumatic fever is virtually negligible in adults, even with completely untreated streptococcal pharyngitis. 1
• This extremely low risk justifies a less aggressive diagnostic approach in adults, including acceptance of negative rapid antigen detection tests without backup throat culture. 1

Recommended Diagnostic Approach for Adults

In adults, a negative rapid antigen detection test (RADT) alone is sufficient to rule out Group A streptococcal infection without requiring confirmatory throat culture. 1

• RADT specificity is ≥95% in adults, making false-positive results rare and allowing confident treatment decisions based on positive results. 1
• The 10–20% false-negative rate of RADTs is acceptable in adults because of the low disease prevalence and virtually zero rheumatic fever risk. 1
• Throat culture confirmation of negative RADTs is explicitly not recommended in adults, as it wastes resources without improving outcomes. 1

When to Test Adults

• Perform RADT only when clinical features suggest bacterial rather than viral pharyngitis: sudden-onset sore throat, fever, tonsillar exudates, tender anterior cervical lymphadenopathy, and absence of viral features (cough, rhinorrhea, hoarseness, conjunctivitis). 1
• Do not test when viral features are present, as these strongly indicate viral etiology and testing will likely identify asymptomatic carriers rather than true infection. 1

Treatment Recommendations for Confirmed Streptococcal Pharyngitis

When RADT is positive, treat with penicillin or amoxicillin for 10 days to prevent the rare complications of suppurative infection and reduce transmission, not to prevent rheumatic fever. 1, 2

First-Line Regimens

• Penicillin V 500 mg orally 2–3 times daily for 10 days 1
• Amoxicillin 50 mg/kg once daily (maximum 1 g) for 10 days 1
• Benzathine penicillin G 1,200,000 units intramuscularly as a single dose (for adherence concerns) 1

Penicillin-Allergic Patients

• Non-anaphylactic allergy: First-generation cephalosporin (e.g., cephalexin) for 10 days 1
• Anaphylactic or immediate-type hypersensitivity: Clindamycin 300 mg three times daily for 10 days, or azithromycin 500 mg once daily for 5 days, or clarithromycin 250 mg twice daily for 10 days 1

Management of Negative Test Results

Withhold all antibiotics when RADT is negative and provide only symptomatic therapy with acetaminophen or ibuprofen. 1, 3

• Most adult pharyngitis is viral and self-limited, resolving within 3–4 days without antibiotics. 1
• Antibiotics provide minimal benefit (shortening symptoms by only 1–2 days) while carrying risks of adverse effects, microbiota disruption, and resistance. 3

Critical Pitfalls to Avoid

• Do not prescribe antibiotics based on clinical appearance alone (e.g., tonsillar exudates or white patches), as these findings occur equally in viral and bacterial infections. 1
• Do not order backup throat cultures after negative RADTs in adults—this is explicitly not recommended and wastes resources. 1
• Do not test or treat asymptomatic household contacts, as up to one-third are asymptomatic carriers and prophylactic treatment does not reduce subsequent infection rates. 1, 4
• Recognize that the clinical algorithm approach without microbiological confirmation results in unacceptably high rates of inappropriate antibiotic use (32–56% accuracy), which is particularly problematic given the low prevalence of streptococcal pharyngitis in adults. 1

Special Considerations

• Adults with occupational exposure to children (teachers, daycare workers) or parents of school-aged children have higher risk of streptococcal pharyngitis but still have extremely low rheumatic fever risk. 1
• Treatment within 9 days of symptom onset still prevents the rare complications, so there is no urgency to treat empirically before test results are available. 1, 4
• Secondary prophylaxis is not indicated in adults unless they have a documented history of acute rheumatic fever from childhood, which would require lifelong prophylaxis based on cardiac involvement. 4, 2