Centor Score Calculator (Modified/McIsaac)

Written by Great Medico

Updated September 25, 2026 •2 min read

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A sore throat can be viral or caused by group A strep, and symptoms overlap. The Modified Centor/McIsaac score organizes a few clinical findings into a short risk score that can help frame whether strep testing should be considered.

What this calculator does

This calculator uses age, tonsillar exudate or swelling, tender anterior cervical nodes, fever above 38°C, and absence of cough. The four clinical findings each add one point. Age then modifies the total, producing the McIsaac-style version of the Centor score.

How to use it

Enter age and mark each finding based on the current examination or reliable history. “Absence of cough” means add the point only when cough is absent. The score is intended for a patient with acute pharyngitis; it should not be applied to unrelated throat symptoms without clinical context.

How the calculation works

The engine adds one point each for tonsillar findings, tender anterior cervical nodes, fever and no cough. It adds one point when age is under 15 and subtracts one point at age 45 or older. The resulting number is labeled as lower, intermediate or higher strep probability.

Example

For the default 25-year-old with no tonsillar exudate, no tender nodes, no fever and no cough, only the “absence of cough” item scores. The result is 1 point, which this tool labels an intermediate probability range.

How to interpret the result

The score estimates pretest probability; it does not identify the organism. Current practice often relies on rapid antigen testing and/or throat culture when group A strep is suspected, with the testing approach depending on age and setting. A high score is not the same as a positive strep test.

Limitations and notes

The age adjustment is a simplified McIsaac rule, and clinical recommendations differ across guidelines and populations. Viral features, local epidemiology and complications are not captured. Seek clinical care for severe symptoms, breathing or swallowing difficulty, dehydration, a concerning rash or persistent illness.