What are the Centor criteria for diagnosis of Group A beta-hemolytic streptococcus (GABHS) pharyngitis?

The Centor Criteria for Diagnosis of Group A Beta-Hemolytic Streptococcus

The Centor criteria consist of four clinical features: fever (by history), tonsillar exudates, tender anterior cervical adenopathy, and absence of cough. 1

Scoring System and Risk Stratification

The Centor criteria help stratify patients based on their likelihood of having Group A beta-hemolytic streptococcal (GABHS) pharyngitis:

Number of Criteria Present	Risk of GABHS Infection
4	51-56%
3	28-35%
2	11-17%
1	5-10%
0	1-2.5%

2, 1

Modified Centor Score

The original Centor score was later modified to include age as a criterion, creating the Modified Centor Score 2:

• Age 3-14 years: +1 point
• Age 15-44 years: 0 points
• Age ≥45 years: -1 point
• Fever (>38°C/100.4°F): +1 point
• Absence of cough: +1 point
• Tonsillar exudates: +1 point
• Tender anterior cervical adenopathy: +1 point

Clinical Application Algorithm

1. Calculate the Centor or Modified Centor score for all patients presenting with sore throat

2. For patients with score 0-1:

   • Low risk of GABHS (≤10%)
   • No testing or antibiotics recommended
   • Provide symptomatic treatment only 1

3. For patients with score 2-3:

   • Intermediate risk of GABHS (11-35%)
   • Perform rapid antigen detection test (RADT)
   • Treat only if RADT is positive 1, 3

4. For patients with score 4:

   • High risk of GABHS (>50%)
   • Options include:
     • Empiric antibiotic treatment without testing
     • RADT confirmation before treatment 1

Important Clinical Considerations

• The Centor criteria were originally validated in adults, while the Modified Centor score has been validated in both adults and children 2, 1

• Clinical features that suggest viral etiology (against GABHS) include: conjunctivitis, cough, hoarseness, coryza, anterior stomatitis, discrete ulcerative lesions, viral exanthem, and diarrhea 2, 1

• Even with all four Centor criteria present, the positive predictive value is still relatively low (≤80%), highlighting the importance of confirmatory testing 1

• Proper throat swab technique is crucial: samples should be obtained from both tonsils (or tonsillar fossae) and the posterior pharyngeal wall 2, 1

Diagnostic Testing Recommendations

• RADT has high specificity (≥95%) but variable sensitivity (around 90%) compared to throat culture 2

• Throat cultures remain the gold standard for diagnosis but have the disadvantage of delayed results (18-24 hours) 2

• The American College of Physicians recommends that patients with fewer than 3 Centor criteria do not need to be tested for GABHS 1

• RADT sensitivity increases with higher Centor scores, making testing more reliable in patients with more clinical features 1

Common Pitfalls to Avoid

• Overdiagnosis: Relying solely on clinical features without using the Centor criteria can lead to unnecessary antibiotic use, as GABHS causes only 5-15% of pharyngitis cases in adults and 15-30% in children 4

• Inappropriate testing: Testing patients with 0-1 Centor criteria is not recommended as the likelihood of GABHS is very low 1, 3

• Inadequate sampling: Poor swabbing technique can significantly reduce test sensitivity 2

• Ignoring recent antibiotic use: Recent antibiotic use can lead to false-negative culture results 2