What are the criteria for treating a patient suspected of having Group A Streptococcal (GAS) pharyngitis?

Criteria for Treating Group A Streptococcal (GAS) Pharyngitis

Treat with antibiotics only when GAS pharyngitis is confirmed by laboratory testing—either a positive rapid antigen detection test (RADT) or throat culture—because clinical features alone cannot reliably distinguish bacterial from viral pharyngitis. 1

Diagnostic Testing Requirements Before Treatment

When to Test

• Perform throat swab testing (RADT and/or culture) for patients with acute pharyngitis who lack overt viral features such as rhinorrhea, cough, oral ulcers, or hoarseness 1
• Do NOT test patients with clear viral symptoms (cough, rhinorrhea, hoarseness, oral ulcers) as these strongly suggest viral etiology 1
• Do NOT test children under 3 years old routinely, as acute rheumatic fever is rare in this age group and streptococcal pharyngitis is uncommon; exceptions include children with risk factors like an older sibling with GAS infection 1

Testing Algorithm by Age Group

Children and Adolescents:

• Positive RADT = treat immediately (no backup culture needed due to high specificity >95%) 1, 2
• Negative RADT = must perform backup throat culture before withholding antibiotics 1

Adults:

• Positive RADT = treat immediately 1
• Negative RADT = backup culture is not routinely necessary due to low GAS incidence and exceptionally low acute rheumatic fever risk in adults 1
• Physicians seeking maximum sensitivity may continue using backup cultures 1

Common Pitfall to Avoid

Never prescribe antibiotics based on clinical presentation alone without laboratory confirmation, as most sore throats are viral and empiric treatment leads to unnecessary antibiotic exposure, resistance development, and adverse effects without benefit 3

Treatment Criteria Once GAS is Confirmed

First-Line Antibiotic Selection

Penicillin or amoxicillin is the mandatory first choice for patients without penicillin allergy, based on narrow spectrum, safety, low cost, and zero documented resistance worldwide 1, 3

Specific Dosing:

• Penicillin V: 500 mg orally twice daily for 10 days (adults) 3, 4
• Amoxicillin: 500 mg orally twice daily for 10 days (adults and children >40 kg) 3, 5
• Amoxicillin: 25 mg/kg/day divided every 12 hours for mild/moderate infections or 45 mg/kg/day divided every 12 hours for severe infections (children <40 kg) 5

The full 10-day course is non-negotiable to eradicate the organism and prevent acute rheumatic fever, even though symptoms typically resolve in 3-4 days 1, 3

Penicillin-Allergic Patients

For non-anaphylactic penicillin allergy:

• First-generation cephalosporin (e.g., cephalexin 500 mg twice daily) for 10 days 1, 3

For anaphylactic/immediate-type penicillin allergy:

• Clindamycin 300 mg three times daily for 10 days 1, 3
• Clarithromycin for 10 days 1
• Azithromycin 500 mg once daily for 5 days (acceptable but not preferred due to 5-8% macrolide resistance rates) 1, 3

Critical Caveat

Never use cephalosporins in patients with anaphylactic penicillin reactions due to 10% cross-reactivity risk 3

Who Should NOT Be Treated

Asymptomatic Contacts

• Do NOT perform diagnostic testing or provide empiric treatment to asymptomatic household contacts of GAS pharyngitis patients 1

Post-Treatment Follow-Up

• Do NOT perform routine follow-up throat cultures or RADT for asymptomatic patients who completed appropriate therapy 1
• Most asymptomatic patients with positive post-treatment cultures are chronic carriers, not treatment failures 1, 6
• Follow-up testing may be considered only in special circumstances (e.g., history of rheumatic fever, outbreak situations) 1

Chronic Carriers

• Chronic carriers (up to 20% of school-aged children during winter/spring) have GAS in their throats without immunologic reaction 6
• Carriers are at low risk for complications, unlikely to spread infection, and generally do not require antimicrobial therapy 7, 6
• Consider carrier state when patients have recurrent positive tests with viral symptoms (congestion, cough, ear pain) 6

Adjunctive Symptomatic Treatment

Pain and fever management should be provided regardless of antibiotic use:

• Ibuprofen 400-600 mg every 6-8 hours or acetaminophen 650-1000 mg every 6 hours for moderate to severe symptoms 1, 3
• Avoid aspirin in children due to Reye's syndrome risk 1
• Do NOT use corticosteroids as adjunctive therapy 1

Treatment Failure and Recurrent Episodes

If symptoms persist after completing appropriate therapy:

• Perform repeat throat culture to distinguish true treatment failure from carrier state with concurrent viral infection 7, 6
• Consider alternative antibiotics if culture remains positive: clindamycin, amoxicillin-clavulanate (80-90 mg/kg/day of amoxicillin component), or first-generation cephalosporin 1, 6
• Evaluate for non-compliance, new infection from contacts, macrolide resistance (if macrolide was used), or suppurative complications 6

For multiple recurrent episodes:

• Distinguish between repeated true infections versus chronic carrier experiencing viral infections 1
• Consider testing and treating family members if "ping-pong" transmission is suspected 6
• Tonsillectomy may be considered for rare patients with persistent frequent symptomatic episodes without alternative explanation 1