Likelihood of bacterial pharyngitis (Group A Strep).
Clinical Findings
Strep Probability
Centor Score0Points
Probability5 - 10%Strep Positivty
Recommendation:
No testing or antibiotics required.
Strep throat is most common in school-age children. Viral infections are more common in adults.
About this calculator
Overview
The Centor score (modified for age by McIsaac) is a tool used to estimate the probability that a sore throat is caused by Group A Streptococcus. It helps clinicians decide which patients should receive a rapid antigen test, a throat culture, or immediate antibiotic therapy.
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Pro Tips
Check for posterior cervical lymph nodes, which might suggest mononucleosis instead of Strep.
Viral causes of sore throat often include cough, rhinorrhea, and hoarseness.
Antibiotics are primarily given to prevent complications like rheumatic fever, not just to shorten symptoms.
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Fun Facts
"A low score (0-1) has a very high negative predictive value (up to 95%)."
"The score was developed primarily to reduce unnecessary antibiotic prescriptions for viral sore throats."
"Modified (McIsaac) score adds age as a factor because Strep is more common in children."
"Scarlet fever rash or known exposure to Strep increases clinical suspicion regardless of the score."
Formula: Points (+1 to -1) are assigned for physical findings and patient age.
