GAS Pharyngitis Overview

Overview

This lecture reviews the diagnosis, management, and complications of Group A Streptococcal (GAS) pharyngitis, emphasizing evidence-based testing and treatment, and recognizing higher risks in Indigenous and vulnerable populations.

Epidemiology & Clinical Presentation

• GAS pharyngitis is the most common bacterial cause of acute pharyngitis in children ages 5–11, especially in winter and spring.
• Asymptomatic carriage occurs in 11–15% of children under 5, posing low transmission and complication risks.
• Key symptoms include fever >38°C, sore throat, tender anterior cervical lymph nodes, no cough/rhinorrhea, and inflamed/purulent tonsils.
• Symptoms typically resolve in 4–5 days without treatment.

Complications & Disease Burden

• GAS pharyngitis can cause suppurative (abscess, sepsis) and non-suppurative (post-streptococcal glomerulonephritis, acute rheumatic fever [ARF]) complications.
• Antibiotic treatment prevents ARF and suppurative complications but not glomerulonephritis.
• ARF and rheumatic heart disease (RHD) are rare in high-income countries but more common in Indigenous populations due to social determinants of health.

Diagnosis & Testing

• Throat swab cultures are the gold-standard; rapid antigen detection tests (RADT) are highly specific and quicker but less sensitive.
• Negative RADT results in high ARF risk settings should be confirmed by culture.
• Testing is not indicated for children under 3 unless during outbreaks or with scarlet fever suspicion.
• Anti-streptolysin O titer (ASOT) is not recommended for diagnosis.

Treatment

• Treat within 9 days of onset to prevent ARF and complications.
• First-line therapy: 10 days of penicillin V or amoxicillin (amoxicillin can be dosed once daily).
• Non-anaphylactic penicillin allergy: cephalexin or oral amoxicillin challenge.
• Anaphylactic penicillin allergy: clarithromycin, azithromycin, or clindamycin (check for local resistance).
• Symptomatic management with acetaminophen or ibuprofen; corticosteroids generally not recommended.

Special Populations & Recurrent Infections

• Higher suspicion and possibly broader testing/treatment for children in high-risk communities (e.g., Indigenous, crowded housing, remote areas).
• Chronic GAS carriage is common and not typically associated with complications; treat carriers only in special situations.
• Trial of eradication therapy may be attempted for persistent or outbreak cases.

Recommendations

• Test children with moderate to severe sore throat, fever, no cough/rhinorrhea, and inflamed/purulent tonsils.
• Confirm GAS by RADT/culture before antibiotics in low-risk populations.
• Empiric treatment may be necessary in high-risk settings with limited testing.

Key Terms & Definitions

• GAS (Group A Streptococcus) — bacteria causing strep throat and other complications.
• ARF (Acute Rheumatic Fever) — inflammatory disease following GAS infection, potentially causing heart damage.
• RHD (Rheumatic Heart Disease) — chronic heart valve damage due to ARF.
• RADT (Rapid Antigen Detection Test) — quick test for GAS with high specificity.
• CENTOR score — clinical tool to help determine likelihood of GAS pharyngitis.

Action Items / Next Steps

• Practice applying CENTOR criteria in hypothetical cases.
• Review antibiotic dosing tables for GAS pharyngitis.
• Read about special considerations for ARF risk in Indigenous communities.