What are the Centor criteria for diagnosing streptococcal pharyngitis?

Centor Criteria for Diagnosing Streptococcal Pharyngitis

The Centor criteria consist of four clinical features: fever by history, tonsillar exudates, tender anterior cervical adenopathy, and absence of cough, which help identify patients with higher likelihood of group A streptococcal pharyngitis. 1

Components of the Centor Criteria

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

Clinical Application

When to Use the Criteria

• The Centor criteria are most useful for identifying patients who have a low probability of streptococcal pharyngitis and therefore do not need testing or antibiotics 1
• These criteria help differentiate between viral and bacterial causes of pharyngitis, as clinical features alone cannot definitively diagnose group A streptococcal pharyngitis 2

Interpretation of Scores

• Patients with fewer than 3 Centor criteria have a low probability of streptococcal pharyngitis and generally do not need testing 1
• Patients with 3-4 Centor criteria have a higher likelihood of streptococcal infection and should be considered for rapid antigen testing (RAT) 1
• The presence of clinical features suggestive of viral etiology (conjunctivitis, coryza, cough, diarrhea) strongly argues against streptococcal pharyngitis 2

Diagnostic Approach Based on Centor Score

Low Score (0-2 criteria)

• Testing is generally not necessary 1
• Antibiotics should not be used in these patients 2, 1
• These patients likely have viral pharyngitis 2

High Score (3-4 criteria)

• Consider rapid antigen detection testing (RADT) 1
• If RADT is performed, throat culture is not necessary after a negative RADT in both children and adults 1
• If antibiotics are indicated based on testing, penicillin V for 10 days is the recommended first-line treatment 2, 1

Limitations and Considerations

• The Centor criteria have a relatively low positive predictive value for determining the presence of group A streptococcal infection 1, 3
• The utility of Centor criteria appears lower in children than in adults due to different clinical presentations of sore throat in younger patients 1, 4
• Even with a high Centor score (3 or 4 criteria), streptococcal pharyngitis cannot be diagnosed with certainty without confirmatory testing 3
• The high negative predictive value makes the diagnosis of non-streptococcal pharyngitis more accurate 3

Important Clinical Pitfalls

• Relying solely on clinical criteria without confirmatory testing can lead to overtreatment with antibiotics 2
• The signs and symptoms of streptococcal and non-streptococcal pharyngitis overlap too broadly for diagnosis to be made with certainty on clinical grounds alone 2
• In children, the Centor criteria are less reliable - a study showed no significant difference in the prevalence of Group A streptococcus for different Centor scores within pediatric age groups 4
• The prevalence of streptococcal pharyngitis is higher in children aged 5-15 years (15-30%) compared to adults (5-10%), which affects the predictive value of the criteria 5

Confirmatory Testing Recommendations

• Throat culture on sheep blood agar remains the gold standard for confirming group A streptococcal pharyngitis 2
• Proper specimen collection technique is crucial - samples should be obtained from both tonsils (or tonsillar fossae) and the posterior pharyngeal wall 2
• Rapid antigen detection tests provide results more quickly and can be used for initial testing, especially in patients with 3-4 Centor criteria 1