How should I evaluate and manage acute pharyngitis, including criteria for rapid streptococcal testing and antibiotic therapy?

Evaluation and Management of Acute Pharyngitis

For adults with acute pharyngitis, perform rapid antigen detection testing (RADT) only when clinical features suggest bacterial infection (using Centor criteria), and accept a negative RADT as definitive without backup culture; for children and adolescents, always confirm negative RADT results with throat culture before withholding antibiotics. 1, 2

Clinical Assessment and Testing Strategy

When to Test for Group A Streptococcus

Do not test patients who present with clear viral features, as these strongly indicate non-streptococcal etiology 1, 2:

• Cough, rhinorrhea (runny nose), or hoarseness
• Conjunctivitis (pink eye)
• Diarrhea
• Discrete oral ulcers or viral rash

Use the Centor criteria to guide testing decisions in patients without obvious viral features 1, 3:

• Fever (history of or present)
• Tonsillar exudates (white patches on tonsils)
• Tender anterior cervical lymphadenopathy (swollen, painful neck glands)
• Absence of cough

Testing Algorithm by Centor Score

0-1 Centor criteria: No testing needed—likelihood of strep is too low to justify testing 1, 3

2 Centor criteria: Perform RADT; treat only if positive 1, 3

3-4 Centor criteria: Two acceptable approaches 1, 3:

• Perform RADT and treat if positive (preferred to reduce antibiotic overuse)
• Consider empiric antibiotics in adults (though testing is still preferred)

Age-Specific Testing Considerations

Children under 3 years: Do not test or treat for strep throat unless an older sibling has confirmed GAS infection, as strep pharyngitis and rheumatic fever are extremely rare in this age group 2, 4

Children and adolescents (3-18 years): 1, 2

• Perform RADT when clinical features suggest possible strep
• Always send backup throat culture if RADT is negative, because rapid tests miss 10-20% of true infections
• Treatment can be safely delayed until culture results return (within 9 days of symptom onset) and still prevent rheumatic fever

Adults: 1, 2

• Perform RADT when clinical features suggest possible strep
• Do not perform backup throat culture after negative RADT—the negative result is sufficient due to low disease prevalence (5-10%) and extremely low rheumatic fever risk in adults
• The high specificity (≥95%) of RADT makes false positives rare

Common Pitfalls to Avoid

Testing asymptomatic contacts: Never test or treat household contacts of patients with strep throat, even with recurrent infection history—up to one-third of households include asymptomatic GAS carriers who do not require treatment 2, 5

Overtesting based on appearance alone: White patches and exudate occur with both viral and bacterial infections and cannot reliably distinguish between them without laboratory confirmation 6

Misinterpreting test sensitivity: The 80-90% sensitivity of RADT means it misses 10-20% of true infections in children, which is why backup culture is mandatory in pediatric patients 1, 2

Testing too early after exposure: If testing an exposed individual who develops symptoms, test immediately; if testing must be done on an asymptomatic exposed person, wait at least 5 days post-exposure to minimize false negatives 2

Antibiotic Therapy for Confirmed Strep Throat

First-Line Treatment

Penicillin remains the treatment of choice due to proven efficacy, safety, narrow spectrum, and low cost—penicillin-resistant GAS has never been documented 1, 4

Dosing options: 1

• Oral penicillin V: 250 mg 2-3 times daily for children <27 kg; 500 mg 2-3 times daily for children ≥27 kg and adults, for 10 days
• Oral amoxicillin: 50 mg/kg once daily (maximum 1 g) for children; often preferred in young children due to better taste acceptance
• Intramuscular benzathine penicillin G: Single dose for patients unlikely to complete 10-day oral course

Alternative Antibiotics

For non-anaphylactic penicillin allergy: First-generation cephalosporins are acceptable 1, 6

For immediate (anaphylactic) penicillin hypersensitivity: 1, 6

• Clindamycin: 20 mg/kg/day divided in 3 doses (maximum 1.8 g/day)
• Azithromycin: 12 mg/kg once daily (maximum 500 mg)
• Clarithromycin

Treatment duration: 10 days is required for penicillin to optimize pharyngeal eradication and prevent rheumatic fever 1

Management of Negative Test Results

Adults with Negative RADT

Withhold antibiotics entirely—a negative RADT is definitive in adults 1, 6, 5

Provide symptomatic treatment only: 1, 6

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

Key point: Antibiotics shorten sore throat duration by only 1-2 days, with number needed to treat of 6 at 3 days and 21 at 1 week 6, 5

Children with Negative RADT

Send backup throat culture before making final treatment decisions 1, 2, 5

While awaiting culture results: 6

• Provide analgesics/antipyretics for symptom relief
• Withhold antibiotics until culture results available
• If culture returns positive, initiate antibiotics—treatment within 9 days of symptom onset still prevents rheumatic fever

Follow-Up and Special Circumstances

Do not perform routine post-treatment testing in asymptomatic patients who completed appropriate antibiotic therapy—a positive test cannot distinguish between carrier state and active infection 1, 6

Consider follow-up testing only in special circumstances: 1, 6

• Multiple recurrent episodes with positive cultures at short intervals (to distinguish true infections from carrier state with viral superinfection)
• History of acute rheumatic fever
• Outbreaks in closed settings where continued transmission is a concern

Recurrent pharyngitis management: If multiple episodes occur, certain antibiotics with higher pharyngeal eradication rates (clindamycin, amoxicillin-clavulanate) may be beneficial, though compliance with initial therapy should be assessed first 1