What are the Centor criteria for diagnosing streptococcal (strep) pharyngitis?

Centor Criteria for Diagnosing Streptococcal Pharyngitis

The modified Centor criteria for diagnosing streptococcal pharyngitis include four clinical features: fever by history, tonsillar exudates, tender anterior cervical adenopathy, and absence of cough. 1

Components of the Centor Criteria

The Centor criteria consist of four specific clinical findings that help determine the likelihood of group A streptococcal pharyngitis:

1. Fever by history (temperature >38°C/100.4°F)
2. Tonsillar exudates (white or yellow patches on tonsils)
3. Tender anterior cervical adenopathy (swollen, painful lymph nodes in the front of the neck)
4. Absence of cough

Each criterion, when present, adds one point to the score, resulting in a total score ranging from 0 to 4.

Clinical Application and Interpretation

The Centor score helps stratify patients based on their likelihood of having streptococcal pharyngitis:

• Score 0-1: Low risk of streptococcal infection (≤10%)

  • No testing or antibiotics recommended 1

• Score 2-3: Intermediate risk of streptococcal infection

  • Rapid antigen detection test (RADT) recommended
  • Treat only if RADT is positive 1, 2

• Score 4: High risk of streptococcal infection (>50%)

  • Some guidelines suggest empiric treatment without testing
  • Others recommend RADT confirmation before treatment 1

Diagnostic Accuracy and Limitations

The Centor criteria have important limitations to consider:

• The positive predictive value is relatively low, even with all four criteria present (≤80%) 1
• The criteria are more reliable in adults than in children 1
• They cannot differentiate between streptococcal carriers with concurrent viral pharyngitis and true streptococcal infections 1
• The sensitivity of the RADT increases with higher Centor scores (from 60.9% with one criterion to 95.8% with all four criteria) 3

Integration with Testing Strategy

The American College of Physicians and CDC recommend:

• Patients with fewer than 3 Centor criteria do not need to be tested for group A streptococcus 1
• For patients with 2 or more criteria, either:
  • Test with RADT and treat only if positive, or
  • Treat empirically only those with 3-4 criteria without testing 2

Clinical Pearls

• Symptoms suggesting viral etiology (and against strep) include: conjunctivitis, cough, hoarseness, coryza, anterior stomatitis, discrete ulcerative lesions, viral exanthem, and diarrhea 1
• Proper throat swab technique is crucial: samples should be obtained from both tonsils (or tonsillar fossae) and the posterior pharyngeal wall 1
• The Centor criteria were developed to reduce unnecessary antibiotic use while identifying patients who would benefit from treatment 3, 2

By using the Centor criteria appropriately, clinicians can make more informed decisions about testing and treatment for streptococcal pharyngitis, thereby improving antibiotic stewardship while ensuring appropriate care for patients with bacterial infections.