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Centor Score (Modified/McIsaac) for Strep Pharyngitis
Centor Score (Strep)
Assesses the likelihood of Group A strep pharyngitis
Centor Score (Modified/McIsaac) for Strep Pharyngitis
Centor Score (Strep)
Assesses the likelihood of Group A strep pharyngitis
Instructions
The Centor Score is a clinical decision tool used to estimate the probability of streptococcal pharyngitis (strep throat) in patients with sore throat symptoms. It guides testing and antibiotic treatment decisions.
Overview
When to use
Why use
Evidences
Interpretation
Centor Score | Probability of Strep (%) |
0–1 | <10% |
2–3 | 11–35% |
4 | >50% |
(Note: McIsaac modification adjusts score by age: +1 for age 3–14, 0 for age 15–44, –1 for age ≥45)
The Centor Score (and its age‑adjusted McIsaac modification) is a 4‑item clinical rule to estimate the probability of group A streptococcal (GAS) pharyngitis and guide testing; large external validations show only fair discrimination, so scores are best used to triage who needs RADT/culture rather than to prescribe empirically.
https://pmc.ncbi.nlm.nih.gov/articles/PMC3627733/
Low scores (0–1) suggest no testing; intermediate/high scores warrant RADT and/or culture per guideline pathways; empiric antibiotics based solely on score are discouraged due to poor specificity.
https://pubmed.ncbi.nlm.nih.gov/15069046/
Large retail‑clinic validation (n≈206,870 encounters) confirmed monotonic increases in GAS positivity with higher Centor/McIsaac scores and supported their role in selecting patients for testing, but not as stand‑alone diagnostic tools.
https://pmc.ncbi.nlm.nih.gov/articles/PMC3627733/
Pediatric data show variable accuracy of the modified Centor, with some cohorts reporting low AUCs and emphasizing that individual signs (e.g., petechiae, exudates) have high specificity but limited standalone utility.
https://pubmed.ncbi.nlm.nih.gov/30806362/
A primary‑care meta‑analysis found both Centor and McIsaac provide only fair discrimination (AUC ~0.69–0.71) and are broadly equivalent; positive scores calibrate poorly to actual probability, reinforcing the need for microbiologic testing to rule in disease.
https://pmc.ncbi.nlm.nih.gov/articles/PMC7065683/
Overview
When to use
Why use
Evidences
The Centor Score was developed to help clinicians quickly assess whether a patient presenting with sore throat symptoms is likely to have Group A Streptococcus (GAS) pharyngitis. Since most sore throats are viral and do not require antibiotics, this tool reduces unnecessary testing and treatment. Overuse of antibiotics can contribute to antimicrobial resistance and expose patients to avoidable side effects, making accurate risk stratification critical.
The score evaluates four clinical features: presence of fever, absence of cough, swollen/tender anterior cervical lymph nodes, and tonsillar exudates or swelling. Each criterion scores one point. The higher the score, the greater the likelihood of streptococcal infection. An additional modification, known as the McIsaac Score, adjusts for age (younger patients are more likely to have GAS).
Centor and McIsaac scores are widely used in primary care, emergency departments, and urgent care settings. They allow clinicians to decide whether further testing (such as rapid antigen detection test [RADT] or throat culture) is necessary or if empiric antibiotics should be started. Patients with lower scores typically require no testing or treatment, while those with higher scores are candidates for testing and, if positive, treatment.
Overview
When to use
Why use
Evidences
Interpretation
Centor Score | Probability of Strep (%) |
0–1 | <10% |
2–3 | 11–35% |
4 | >50% |
(Note: McIsaac modification adjusts score by age: +1 for age 3–14, 0 for age 15–44, –1 for age ≥45)
The Centor Score (and its age‑adjusted McIsaac modification) is a 4‑item clinical rule to estimate the probability of group A streptococcal (GAS) pharyngitis and guide testing; large external validations show only fair discrimination, so scores are best used to triage who needs RADT/culture rather than to prescribe empirically.
https://pmc.ncbi.nlm.nih.gov/articles/PMC3627733/
Low scores (0–1) suggest no testing; intermediate/high scores warrant RADT and/or culture per guideline pathways; empiric antibiotics based solely on score are discouraged due to poor specificity.
https://pubmed.ncbi.nlm.nih.gov/15069046/
Large retail‑clinic validation (n≈206,870 encounters) confirmed monotonic increases in GAS positivity with higher Centor/McIsaac scores and supported their role in selecting patients for testing, but not as stand‑alone diagnostic tools.
https://pmc.ncbi.nlm.nih.gov/articles/PMC3627733/
Pediatric data show variable accuracy of the modified Centor, with some cohorts reporting low AUCs and emphasizing that individual signs (e.g., petechiae, exudates) have high specificity but limited standalone utility.
https://pubmed.ncbi.nlm.nih.gov/30806362/
A primary‑care meta‑analysis found both Centor and McIsaac provide only fair discrimination (AUC ~0.69–0.71) and are broadly equivalent; positive scores calibrate poorly to actual probability, reinforcing the need for microbiologic testing to rule in disease.
https://pmc.ncbi.nlm.nih.gov/articles/PMC7065683/
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