McIsaac Score (Modified Centor)
McIsaac score — the age-corrected Centor score for streptococcal pharyngitis.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Age
- 50 years
- Temperature > 38 C
- Yes
- Absence of cough
- Yes
- Tender anterior cervical adenopathy
- Yes
- Tonsillar swelling or exudate
- Yes
Result: McIsaac 3 — group A strep probability ~28-35%; rapid antigen test or throat culture, treat if positive.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- <= 0
- Group A strep probability ~1-2.5%; no testing or antibiotic indicated.
- 1
- ~5-10%; no testing or antibiotic in most adults; culture optional.
- 2-3
- ~11-35%; rapid antigen test or throat culture, treat if positive.
- 4-5
- ~51-53%; rapid antigen test or throat culture, or empiric treatment. It recommends a testing strategy, never an antibiotic order.
What you enter
- Age
- Temperature > 38 C
- Absence of cough
- Tender anterior cervical adenopathy
- Tonsillar swelling or exudate
How this is calculated
McIsaac WJ, White D, Tannenbaum D, Low DE. A clinical score to reduce unnecessary antibiotic use in patients with sore throat. CMAJ. 1998;158(1):75-83. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.