What are the diagnostic criteria and treatment options for a patient presenting with a sore throat suspected to be streptococcal pharyngitis using Centor's criteria?

Centor Criteria for Streptococcal Pharyngitis

What Are the Centor Criteria?

The Centor score is a validated 4-point clinical decision tool that stratifies the probability of group A streptococcal (GAS) pharyngitis in adults with sore throat, using fever by history, tonsillar exudates, tender anterior cervical lymphadenopathy, and absence of cough—with each criterion receiving one point for a maximum score of 4. 1, 2

The Four Components:

• Fever by history (1 point) 3, 1
• Tonsillar exudates (1 point) 3, 1
• Tender anterior cervical lymphadenopathy (1 point) 3, 1
• Absence of cough (1 point) 3, 1

Risk Stratification by Score

The score directly correlates with probability of streptococcal infection 1:

• Score 0: 1-2.5% probability 1
• Score 1: 5-10% probability 1
• Score 2: 11-17% probability 1
• Score 3: 28-35% probability 1
• Score 4: 51-53% probability 1

Clinical Decision Algorithm

For Scores 0-2 (Low Probability):

Do not test or treat with antibiotics—provide symptomatic management only. 3, 1 Patients meeting fewer than 3 Centor criteria do not warrant further testing because the Centor criteria have low positive predictive value for determining GAS infection. 3, 2

• Recommend ibuprofen or acetaminophen for symptom relief 3, 4
• Reassure patients that symptoms typically resolve in less than 1 week without antibiotics 4
• Use ICD-10 code J02.9 (Acute pharyngitis, unspecified) or J02.8 if viral etiology is suspected 4

For Scores 3-4 (Higher Probability):

Perform a rapid antigen detection test (RADT) and treat only if positive. 3, 2 In patients with high likelihood of streptococcal infections (3-4 Centor criteria), physicians should consider using rapid antigen tests. 3, 2

• If RADT is positive, treat with penicillin V for 10 days 1, 2, 5
• If RADT is negative in adults, no throat culture is necessary—the test is sufficient to rule out GAS pharyngitis 3, 2, 4
• If RADT is negative in children/adolescents, confirm with throat culture due to 80-90% sensitivity of rapid tests 4

Testing Technique

Both the posterior pharyngeal wall and both tonsils must be swabbed to optimize test accuracy—improper technique reduces sensitivity and leads to false-negative results. 1, 2

Treatment When Indicated

First-Line Antibiotic:

Penicillin V for 10 days remains the first-line treatment for confirmed GAS pharyngitis. 3, 1, 2, 5 Therapy must be sufficient to eliminate the organism (10-day minimum) to prevent sequelae of streptococcal disease. 5

Alternative Antibiotics:

• For penicillin-allergic patients: first-generation cephalosporins, clindamycin, or macrolides 6
• Azithromycin (12 mg/kg once daily for 5 days in children) has been shown clinically and microbiologically superior to penicillin V at Day 14 and Day 30 7

Symptomatic Management:

• Ibuprofen or acetaminophen for pain and fever relief 3, 4
• Medicated throat lozenges every two hours 6
• Corticosteroids in conjunction with antibiotics can be considered in adults with severe presentations (3-4 Centor criteria), but are not routinely recommended 3

Important Clinical Caveats

Modest Benefits of Antibiotics:

Antibiotics shorten sore throat duration by only 1-2 days, with a number needed to treat of 6 at 3 days and 21 at 1 week. 3, 4 The modest benefits must be weighed against side effects, impact on microbiota, increased antibiotic resistance, medicalization, and costs. 3, 2

Primary Justification for Treatment:

The main reason to treat confirmed streptococcal pharyngitis is prevention of acute rheumatic fever, peritonsillar abscess, and spread during outbreaks—not symptom relief. 3, 4 Evidence suggests antibiotics may prevent complications including acute rheumatic fever (more common in children/adolescents), peritonsillar abscess, and further spread of GAS in outbreaks, but little evidence supports prevention of acute glomerulonephritis. 3

Limitations of Centor Score:

• Even with a score of 4, only about half of patients actually have GAS pharyngitis, highlighting the need for confirmatory testing rather than empiric treatment 1
• The Centor score was validated only in adults, not children—utility appears lower in children due to different clinical presentation of sore throat in early years of life 3, 2
• The modified McIsaac score adds age stratification for broader applicability 1

Red Flags Requiring Urgent Evaluation:

Patients presenting with unusually severe signs and symptoms—difficulty swallowing, drooling, neck tenderness, or swelling—should be evaluated for rare throat infections such as peritonsillar abscess, parapharyngeal abscess, epiglottitis, or Lemierre syndrome. 3

Viral Pharyngitis Indicators:

Patients with sore throat and associated cough, nasal congestion, conjunctivitis, hoarseness, diarrhea, or oropharyngeal lesions (ulcers or vesicles) are more likely to have viral illness and should not have further testing. 3