Diagnosis and Treatment of Strep Throat
Diagnosis
Laboratory confirmation is mandatory for diagnosing strep throat because clinical symptoms of Group A streptococcal pharyngitis and viral pharyngitis overlap too broadly to rely on clinical judgment alone. 1
Diagnostic Testing Algorithm
Use either a rapid antigen detection test (RADT) or throat culture to confirm the presence of Group A streptococci in patients with acute pharyngitis symptoms. 1
For adults with a negative RADT: No confirmatory throat culture is needed—withhold antibiotics entirely. 1, 2, 3
For children and adolescents with a negative RADT: Confirm with a throat culture due to higher prevalence of strep infections and risk of rheumatic fever complications. 1, 2, 3
Test Characteristics
RADTs have excellent specificity (≥95%), meaning positive results are highly reliable and therapeutic decisions can be made with confidence. 1
RADTs have lower sensitivity (80-90%) compared to throat culture, missing 10-20% of true infections, which is why negative results require confirmation in children. 1, 3
Proper swabbing technique is critical: Swab both the posterior pharyngeal wall and tonsils to maximize diagnostic accuracy. 3
Important Diagnostic Pitfalls
Never treat based on clinical symptoms alone without laboratory confirmation—this leads to massive antibiotic overuse since only a minority of pharyngitis cases are actually streptococcal. 1, 2
Do not test children under 3 years old routinely, as Group A streptococcal pharyngitis and rheumatic fever are rare in this age group. 2
Do not test or treat asymptomatic household contacts. 2
Treatment
For Patients WITHOUT Penicillin Allergy
Oral penicillin V or amoxicillin for 10 days is the standard of care and remains the drug of choice. 4, 2, 5
Amoxicillin 50 mg/kg/day once daily (maximum 1000 mg) offers improved adherence with once-daily dosing. 2
Intramuscular benzathine penicillin G (600,000 U for <27 kg; 1,200,000 U for ≥27 kg) as a single dose for patients unlikely to complete oral therapy. 2
The 10-day duration is mandatory to achieve maximal pharyngeal eradication and prevent acute rheumatic fever—shortening the course by even a few days results in appreciable increases in treatment failure rates. 4, 2, 5
For Patients WITH Penicillin Allergy
The treatment choice depends on whether the allergy is immediate/anaphylactic or non-immediate:
Non-Anaphylactic Penicillin Allergy
First-generation cephalosporins are the preferred first-line alternatives with strong, high-quality evidence supporting their efficacy. 1, 4, 2
Cephalexin 20 mg/kg per dose twice daily (maximum 500 mg/dose) for 10 days. 4
Cefadroxil 30 mg/kg once daily (maximum 1 gram) for 10 days. 4
Immediate/Anaphylactic Penicillin Allergy
Patients with immediate hypersensitivity should avoid all beta-lactams, including cephalosporins, due to up to 10% cross-reactivity risk. 4, 3
Clindamycin 7 mg/kg three times daily (maximum 300 mg per dose) for 10 days is the preferred alternative with strong, moderate-quality evidence and only ~1% resistance in the United States. 4, 2
Azithromycin 12 mg/kg once daily (maximum 500 mg) for 5 days is an acceptable alternative due to its prolonged tissue half-life. 4, 2, 6
Clarithromycin 7.5 mg/kg per dose twice daily (maximum 250 mg/dose) for 10 days. 4, 2
Critical Treatment Considerations
Macrolide resistance among Group A Streptococcus is approximately 5-8% in the United States but varies geographically—be aware of local resistance patterns before prescribing azithromycin or clarithromycin. 4, 2
Patients become non-contagious after 24 hours of appropriate antibiotic therapy and can return to school or work. 2, 7
The primary goal of antibiotic treatment is preventing acute rheumatic fever, not just symptom relief—this requires adequate bacterial eradication with a full treatment course. 1, 4, 2
Treatment for Strep-Negative (Viral) Pharyngitis
Withhold antibiotics entirely for patients with negative Group A streptococcal testing. 2, 3
Symptomatic Management
Ibuprofen or acetaminophen for moderate to severe symptoms or high fever, with NSAIDs (ibuprofen) providing superior pain relief compared to acetaminophen in randomized controlled trials. 2
Do not use corticosteroids as adjunctive therapy—they provide only minimal benefit (approximately 5 hours pain reduction) with potential adverse effects. 4, 2
Critical Pitfalls to Avoid
Never use tetracyclines (high resistance rates), sulfonamides, trimethoprim-sulfamethoxazole (do not eradicate Group A Streptococcus), or older fluoroquinolones like ciprofloxacin (limited Group A Streptococcus activity). 2
Do not perform routine follow-up throat cultures after completing therapy in asymptomatic patients. 4, 2
Do not switch antibiotics without microbiological indication—this increases adverse effects without clinical benefit. 3
Do not assume all penicillin-allergic patients cannot receive cephalosporins—only those with immediate/anaphylactic reactions should avoid them. 4
Special Circumstances
If symptoms persist or recur shortly after completing therapy, consider that the patient may be a chronic Group A Streptococcus carrier experiencing viral infections rather than true recurrent streptococcal pharyngitis. 2
Chronic carriers generally do not require antimicrobial therapy, as they are unlikely to spread infection and are at little risk for complications. 4, 2
Treatment of carriers is justified only in special circumstances: community outbreak of rheumatic fever, family history of rheumatic fever, or excessive family anxiety. 2