🦠 McIsaac Score (Modified Centor, Pharyngitis)
Estimate group A strep pharyngitis probability with the McIsaac (modified Centor) score.
Clinical takeaway
Adds age adjustment to Centor criteria.
Loading calculator…
Paste the link in Slack, Teams, X, or LinkedIn — the preview image comes from this page’s Open Graph card.
When to use
Guide rational testing and antibiotic use in sore throat.
How it works
Temp > 38, no cough, tender anterior nodes, tonsillar swelling/exudate each +1; age 3–14 +1, 15–44 0, ≥ 45 −1.
Key points
- Adds age adjustment to Centor criteria.
- Most scores warrant confirmatory RADT/culture, not empiric antibiotics.
- Reduces unnecessary antibiotic prescribing.
References
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Temperature > 38°C | No |
|---|---|
| Absence of cough | Cough present (0) |
| Tender anterior cervical nodes | No |
| Tonsillar swelling/exudate | No |
| Age | 3–14 (+1) |
→McIsaac1
- Strep probability：~5–10%
- Note：Most guidelines recommend confirming with RADT/culture rather than empiric antibiotics, except possibly at the highest scores.
| Temperature > 38°C | Yes (+1) |
|---|---|
| Absence of cough | No cough (+1) |
| Tender anterior cervical nodes | Yes (+1) |
| Tonsillar swelling/exudate | Yes (+1) |
| Age | ≥ 45 (−1) |
→McIsaac3
- Strep probability：~11–28% — consider rapid antigen test/culture
- Note：Most guidelines recommend confirming with RADT/culture rather than empiric antibiotics, except possibly at the highest scores.
Frequently asked questions
- What is McIsaac Score (Modified Centor, Pharyngitis)?
- Estimate group A strep pharyngitis probability with the McIsaac (modified Centor) score.
- How is McIsaac Score (Modified Centor, Pharyngitis) calculated? What is the core formula?
- Temp > 38, no cough, tender anterior nodes, tonsillar swelling/exudate each +1; age 3–14 +1, 15–44 0, ≥ 45 −1.
- When is McIsaac Score (Modified Centor, Pharyngitis) used?
- Guide rational testing and antibiotic use in sore throat.
- What are the key clinical points for McIsaac Score (Modified Centor, Pharyngitis)?
- Adds age adjustment to Centor criteria. Most scores warrant confirmatory RADT/culture, not empiric antibiotics. Reduces unnecessary antibiotic prescribing.
- What are the limits and cautions when using McIsaac Score (Modified Centor, Pharyngitis)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is McIsaac Score (Modified Centor, Pharyngitis) calculated in practice? Can you show a worked example?
- Inputs: Temperature > 38°C No, Absence of cough Cough present (0), Tender anterior cervical nodes No, Tonsillar swelling/exudate No, Age 3–14 (+1) → Result: McIsaac 1（Strep probability: ~5–10%, Note: Most guidelines recommend confirming with RADT/culture rather than empiric antibiotics, except possibly at the highest scores.） Inputs: Temperature > 38°C Yes (+1), Absence of cough No cough (+1), Tender anterior cervical nodes Yes (+1), Tonsillar swelling/exudate Yes (+1), Age ≥ 45 (−1) → Result: McIsaac 3（Strep probability: ~11–28% — consider rapid antigen test/culture, Note: Most guidelines recommend confirming with RADT/culture rather than empiric antibiotics, except possibly at the highest scores.）