Centor and McIsaac score calculator
Likelihood of group A streptococcal pharyngitis, with the McIsaac age adjustment.
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This is a reference implementation of a published formula, provided for use by qualified healthcare professionals. It does not diagnose, does not account for the individual circumstances of any patient, and is not a recommendation for treatment. Confirm every result against your own institutional guidance before acting on it. Clinical judgement always takes precedence over a calculator.
About this calculation
The Centor criteria estimate the probability that a sore throat is group A streptococcal. The McIsaac modification adds an age adjustment, which matters because the base rate is much higher in children and lower in older adults.
Formula
One point each: tonsillar exudate · tender anterior cervical nodes · fever · absence of cough. McIsaac: +1 if age 3–14, −1 if age ≥ 45
- Source
- Centor RM et al. (1981); McIsaac WJ et al., CMAJ (1998)
- Methodology version
- 1.0.0
- Last reviewed
- 2026-10-28
What this does not account for
- The score estimates the probability of a positive test. It does not establish that antibiotics are indicated, which depends on local guidance and the clinical picture.
- It performs poorly under the age of 3, where streptococcal pharyngitis is uncommon and presents differently.
- Most guidance recommends confirming with a rapid antigen test or culture rather than treating on score alone.