Centor and McIsaac score calculator
Answer four questions about a sore throat and choose the age group to get the Centor score and the McIsaac score, which adjusts it for age. They estimate how likely a group A strep infection is. It is an estimate for information, not a diagnosis.
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How to use it
- Choose the age group.
- Tick each sign that is present: swollen or coated tonsils, tender neck nodes, fever above 38 °C and no cough.
- Read the McIsaac score, the usual next step and the plain Centor score.
How the score works
One point each for tonsillar swelling or exudate, tender swollen anterior neck nodes, fever above 38 °C and absence of cough: that is the Centor score (0 to 4). The McIsaac score adds age: +1 for 3–14 years, 0 for 15–44, −1 for 45 or older (−1 to 5).
| McIsaac score |
Usual next step |
| 1 or less |
No test or antibiotic usually needed |
| 2–3 |
Rapid strep test or throat swab |
| 4–5 |
Test; some guidelines allow treatment without waiting |
Worked example
A 10-year-old with fever of 38.6 °C, no cough and normal tonsils: fever 1 + no cough 1 = Centor 2; age 3–14 adds 1, so McIsaac 3, and a strep test is usually advised.
A 50-year-old with swollen tonsils and tender nodes: Centor 2, age −1, McIsaac 1: strep is unlikely.
Tips
- A runny nose, hoarse voice or mouth ulcers point to a virus, even if the score is moderate.
- The score was developed for ages 3 and up; it is not used for babies and toddlers.
- This is an estimate for information, not a diagnosis or a treatment decision.
Frequently asked questions
What is the difference between Centor and McIsaac?
Centor uses the four symptoms only (0 to 4). McIsaac adds a point for ages 3 to 14 and takes one away from age 45, because strep throat is more common in children and less common in older adults. The calculator shows both.
Can the score tell me I have strep throat?
No. Even at the top score many sore throats are viral. The score helps decide who should be tested; only a rapid test or a throat culture shows whether strep is there.
Why not just take antibiotics?
Most sore throats are viral and get better on their own within about a week. Antibiotics do not help viral infections, can cause side effects and add to resistance.
When should I seek care urgently?
If you have trouble breathing or swallowing, are drooling, cannot open your mouth fully, or one side of the throat is much more swollen, see a doctor straight away whatever the score.