Clinical tool
Centor/McIsaac
Likelihood of streptococcal sore throat.
McIsaac age modification
Centor/McIsaac
0/ 5
Select an age group
The McIsaac score includes an age adjustment, so the likelihood cannot be read until age is chosen.
Still to choose: Age.
This score supports risk stratification and should be interpreted alongside the overall clinical context and current treatment guidance.
Score support, not a decision
What this calculates
The Centor score with the McIsaac age modification: the likelihood that a sore throat is due to group A streptococcus, from −1 to 5.
When to use it
In a patient aged 3 or over with an acute sore throat, to decide whether testing is worthwhile.
How to interpret it
Scores of 0 or below and 1 make streptococcal infection unlikely. At 2 to 3 testing is commonly used, and from 4 the probability is about half.
Important limitations
- Even at the top of the scale around half of patients do not have streptococcal infection, so testing is generally preferred to treating on score alone.
- It does not apply to children under 3.
- It does not screen for peritonsillar abscess, epiglottitis or other conditions needing urgent attention.
For practising medics only. Clinical tools support judgement, they do not replace it. Always verify results against current guidelines and the patient in front of you.