How should I diagnose and treat a patient with suspected streptococcal pharyngitis presenting with sore throat, fever, tonsillar exudates, tender anterior cervical lymphadenopathy, and no cough?

Diagnosis and Management of Streptococcal Pharyngitis

Immediate Diagnostic Approach

Your patient meets all four modified Centor criteria (fever, tonsillar exudates, tender anterior cervical lymphadenopathy, absence of cough), placing them at high probability for Group A Streptococcal (GAS) pharyngitis and mandating immediate rapid antigen detection testing (RADT) before prescribing antibiotics. 1

Why Testing Is Mandatory

• Clinical features alone cannot reliably distinguish bacterial from viral pharyngitis, even when all four Centor criteria are present—the positive predictive value ranges only 40-60% in adults 2
• Up to 70% of patients with sore throat receive unnecessary antibiotics, yet only 5-15% of adults actually have GAS pharyngitis 2
• The modified Centor score identifies patients who warrant testing but cannot substitute for microbiologic confirmation 1, 3

Testing Strategy by Age

Adults:

• Perform RADT immediately; a negative result alone is sufficient to rule out GAS without backup throat culture 1, 2
• RADT specificity is ≥95% (false positives are rare) with sensitivity 80-90% 2, 4
• The low prevalence of GAS in adults (5-10%) and extremely low risk of acute rheumatic fever justify accepting the 10-20% false-negative rate 2

Children and adolescents (ages 3-18):

• Perform RADT first, but a negative result must be confirmed with throat culture 2, 4
• The two-step approach is mandatory because GAS prevalence is higher (20-30%) and rheumatic fever risk is greater 2
• Treatment can be delayed 24-48 hours for culture results, as antibiotics started within 9 days of symptom onset still prevent rheumatic fever 2

First-Line Antibiotic Treatment for Confirmed GAS

Penicillin V or amoxicillin for 10 days is the definitive first-line treatment, offering narrow-spectrum activity, proven efficacy in preventing acute rheumatic fever, and minimal adverse effects. 1, 2

Specific Dosing Regimens

Penicillin V:

• Children <27 kg: 250 mg 2-3 times daily for 10 days 2
• Children ≥27 kg and adults: 500 mg 2-3 times daily for 10 days 2

Amoxicillin:

• 50 mg/kg once daily (maximum 1 g) for 10 days 2
• Equally effective as penicillin with better palatability 5

Benzathine penicillin G (intramuscular):

• <27 kg: 600,000 units single dose 2
• ≥27 kg: 1,200,000 units single dose 2
• Reserved for adherence concerns 2

Penicillin-Allergic Patients

Non-anaphylactic allergy:

• First-generation cephalosporin (cephalexin or cefadroxil) for 10 days 1, 2

Anaphylactic or immediate-type hypersensitivity:

• Clindamycin: 20 mg/kg/day divided three times daily (maximum 1.8 g/day) for 10 days 2
• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 2
• Clarithromycin: 15 mg/kg/day divided twice daily for 10 days 2

Management When Testing Is Negative

Withhold all antibiotics and provide only symptomatic treatment when RADT (and culture, if performed) is negative, as the vast majority of these cases are viral and self-limited. 1, 2

Symptomatic Relief

• Ibuprofen or acetaminophen for pain and fever control 1, 2
• Throat lozenges for comfort 2
• Reassurance that symptoms typically resolve in less than 1 week 2

Why Antibiotics Offer Minimal Benefit

• Antibiotics shorten sore throat duration by only 1-2 days 1
• Number needed to treat is 6 at 3 days and 21 at 1 week 1
• The modest benefit is outweighed by adverse effects, microbiota disruption, and resistance promotion 1, 2

Common Pitfalls to Avoid

Do not prescribe antibiotics based on clinical appearance alone:

• Tonsillar exudates and white patches occur in both viral and bacterial infections 2
• Even experienced clinicians cannot reliably distinguish GAS from viral pharyngitis without laboratory confirmation 6

Do not test or treat asymptomatic household contacts:

• Up to one-third of household members are asymptomatic GAS carriers 2
• Prophylactic treatment does not reduce subsequent infection rates 2

Do not perform routine follow-up testing after completing therapy:

• Post-treatment cultures in asymptomatic patients often reflect carrier status rather than treatment failure 2
• Follow-up testing is not indicated unless special circumstances exist (e.g., history of rheumatic fever, outbreak settings) 2

Do not order backup throat culture in adults with negative RADT:

• This wastes resources and offers no clinical benefit 2
• The single negative RADT is definitive in adults 2

Special Considerations

Children under 3 years:

• Routine GAS testing is not indicated because acute rheumatic fever is rare and GAS pharyngitis incidence is low 2, 4
• Consider testing only when an older sibling has confirmed GAS infection 4

Timing of antibiotic initiation:

• Treatment within 9 days of symptom onset prevents acute rheumatic fever 2
• This allows time for culture confirmation without compromising outcomes 2

Recurrent pharyngitis:

• Consider chronic GAS carriage with superimposed viral infections rather than repeated true GAS infections 2
• Multiple positive cultures at short intervals may reflect carrier state, not treatment failure 2