The Role of Centor Score in Diagnosing Streptococcal Pharyngitis
The Centor score is a validated clinical decision rule that effectively stratifies the risk of Group A Streptococcal (GAS) pharyngitis and should guide testing and treatment decisions in patients presenting with sore throat. 1
Components of the Centor Score
The Centor score consists of four clinical features, with one point assigned for each:
- Fever by history (temperature >38°C/100.4°F) 2, 1
- Tonsillar exudates 2, 1
- Tender anterior cervical adenopathy 2, 1
- Absence of cough 2, 1
Risk Stratification Based on Centor Score
The Centor score effectively stratifies patients according to their likelihood of GAS pharyngitis:
- Score of 0: 2.5% risk of GAS infection 2
- Score of 1: 5-10% risk of GAS infection 2
- Score of 2: 11-17% risk of GAS infection 2
- Score of 3: 28-35% risk of GAS infection 2
- Score of 4: 51-53% risk of GAS infection 2
Modified Centor Score
The original Centor score was later modified to include age as an additional criterion:
This modification improves diagnostic accuracy by accounting for the higher prevalence of GAS in children and lower prevalence in older adults 1, 3.
Testing Recommendations Based on Centor Score
- Score 0-1: No testing or antibiotics recommended (low probability of GAS) 1, 4
- Score 2: Consider rapid antigen detection test (RADT) 1, 5
- Score 3-4: Perform RADT; high probability of GAS infection 1, 5
Diagnostic Accuracy and Validation
- The Centor score has been validated in large-scale studies with consistent performance across diverse populations 3
- A large validation study of 206,870 patients confirmed the predictive value of both Centor and McIsaac scores 3
- For patients with a Centor score of 4, approximately 57% tested positive for GAS 3
- For patients with a Centor score of 0, only 7% tested positive for GAS 3
Role of Rapid Antigen Detection Tests (RADT)
- RADTs have high specificity (≥95%) but variable sensitivity (80-90%) compared to throat culture 6
- The accuracy of RADTs increases when performed in patients with higher Centor scores 2
- For adults with a negative RADT, backup throat culture is generally not necessary 6
- For children with a negative RADT, backup throat culture is recommended due to higher prevalence of GAS and risk of complications 6
Common Pitfalls to Avoid
- Treating based on clinical symptoms alone without laboratory confirmation leads to antibiotic overuse 6, 4
- Testing patients with clear viral symptoms unnecessarily increases healthcare costs 4
- Overreliance on the Centor score without considering age-specific modifications may reduce accuracy 1
- The Centor criteria have lower utility in children under 3 years due to different clinical presentations 1
- Improper swabbing technique can reduce test accuracy; both posterior pharyngeal wall and tonsils should be swabbed 2
Antibiotic Stewardship Considerations
- Antibiotics should not be prescribed for patients with low Centor scores (0-2) 1, 7
- For patients with scores 3-4, benefits of antibiotics should be weighed against risks of side effects and antimicrobial resistance 1
- Studies in developing countries show high rates of inappropriate antibiotic prescribing for pharyngitis that could be reduced with proper use of Centor/McIsaac scores 7, 8
The Centor score remains a valuable clinical tool for the initial assessment of patients with suspected streptococcal pharyngitis, helping clinicians make evidence-based decisions about testing and treatment while promoting antibiotic stewardship.