Clinical tool
Centor/McIsaac
Likelihood of streptococcal pharyngitis.
Age
McIsaac age modification
Score
0/ 5
Very low likelihood
Roughly 1–2.5% chance of streptococcal infection. No testing or antibiotics — treat symptomatically.
Answer every graded item above for a complete score.
Even at the top of the scale, around half of patients do not have streptococcal infection — which is why most guidelines recommend testing rather than treating on score alone. Antibiotics in sore throat shorten symptoms by roughly a day; the main justification is preventing rheumatic fever, which is far more relevant in high-incidence settings and should shape local practice. This score does not apply to children under 3, and does not assess for peritonsillar abscess, epiglottitis or other causes 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.