What are the criteria for prescribing antibiotics to a patient with acute pharyngitis?

Criteria for Prescribing Antibiotics in Acute Pharyngitis

Antibiotics should only be prescribed for acute pharyngitis when Group A Streptococcal (GAS) infection is confirmed by testing in patients with clinical features suggesting bacterial infection, specifically those meeting 3-4 modified Centor criteria or those with 2 criteria and a positive rapid antigen detection test (RADT). 1

Clinical Screening: Modified Centor Criteria

Use the modified Centor criteria to stratify patients and determine who requires testing 1:

Score 1 point for each:

• Temperature ≥38°C (fever by history) 1
• Absence of cough 1
• Tender anterior cervical adenopathy 1
• Tonsillar swelling or exudates 1

Management based on score:

• 0-1 criteria: Do NOT test or treat with antibiotics—viral etiology is most likely 1, 2
• 2-3 criteria: Perform RADT; prescribe antibiotics ONLY if positive 1
• 4 criteria: Either perform RADT and treat if positive, OR treat empirically without testing 1, 2

The presence of viral symptoms (cough, nasal congestion, conjunctivitis, hoarseness, diarrhea, or oral ulcers/vesicles) strongly suggests viral pharyngitis and testing should NOT be performed 1.

Diagnostic Testing Approach

For Adults:

• A negative RADT is sufficient to rule out GAS pharyngitis—no backup throat culture is needed 1, 3
• The specificity of RADT is ≥95% and sensitivity is 80-90% 3
• Adults have only 5-10% prevalence of GAS pharyngitis and extremely low risk of acute rheumatic fever 3

For Children and Adolescents:

• A negative RADT must be confirmed with throat culture before withholding antibiotics 4, 3
• Children ages 5-15 have higher GAS prevalence (20-30%), but 70-80% of cases remain viral 3
• Treatment can be delayed until culture results return, as initiating antibiotics within 9 days of symptom onset still prevents acute rheumatic fever 4, 3

Throat cultures take 2-3 days and cannot differentiate acute infection from asymptomatic carriage, limiting their utility for initial antibiotic decisions 1.

Antibiotic Selection When Indicated

First-line treatment:

• Penicillin V or amoxicillin for 10 days remains the standard of care 1, 4
• Penicillin is chosen for its proven efficacy, narrow spectrum, safety, and low cost 1
• GAS has shown no resistance to penicillin over five decades 1

For penicillin-allergic patients:

• First-generation cephalosporins, clindamycin, or clarithromycin for 10 days 1, 4
• Azithromycin for 5 days is an alternative, though it achieves lower bacteriologic eradication rates (31-38% vs. 68-81% with penicillin) without increased clinical sequelae 5, 6

While newer antibiotics (cephalosporins, macrolides) show statistically higher cure rates than penicillin, the clinical differences are minimal and not clinically relevant 1. Short-course penicillin (≤5 days) is less effective than 10-day courses for both clinical cure and bacteriologic eradication 7.

Common Pitfalls to Avoid

Do NOT prescribe antibiotics based on:

• Clinical appearance alone—white patches and exudates occur with viral infections and cannot reliably distinguish bacterial from viral causes 3
• Physician judgment without testing—this leads to 60-70% unnecessary antibiotic prescriptions when only 10-20% of adults actually have GAS pharyngitis 1, 3

Do NOT test or treat:

• Asymptomatic household contacts, even with history of recurrent infections—up to one-third of households include asymptomatic GAS carriers who do not require treatment 4, 3
• Children under 3 years old, as GAS pharyngitis is rare in this age group 3

Do NOT perform:

• Routine post-treatment cultures in asymptomatic patients—a positive test after appropriate treatment likely reflects carrier state, not treatment failure 3

Benefits of Antibiotic Treatment

When GAS infection is confirmed, antibiotics provide modest symptomatic benefit (shortening sore throat duration by 1-2 days, with number needed to treat of 6 at day 3 and 21 at week 1) 1, 3. The primary justification for treatment is prevention of suppurative complications (peritonsillar abscess), acute rheumatic fever, and transmission during outbreaks 1, 3. Antibiotics do NOT prevent post-streptococcal glomerulonephritis 1, 3.

Symptomatic Management for All Patients

Regardless of antibiotic decision, offer all patients with pharyngitis 1, 4, 3:

• Analgesics/antipyretics (acetaminophen or ibuprofen)
• Throat lozenges
• Warm salt water gargles
• Reassurance that symptoms typically resolve in less than 1 week

The modest benefits of antibiotics (1-2 days symptom reduction) must be weighed against side effects, impact on microbiota, increased antimicrobial resistance, medicalization, and costs 1.