What makes this "modified" Centor vs. original?

The original Centor Score (1981) uses four criteria and ranges 0–4. McIsaac modified it in 1998 by adding an age factor: +1 for ages 3–14 (peak strep prevalence in children), 0 for ages 15–44, and −1 for ages 45 and older (lower GAS prevalence). This extends the range to −1 to 5 and improves accuracy across age groups.

Does a high score confirm strep throat?

No. A high score raises pre-test probability but does not confirm GAS. Use RADT, molecular testing, and/or culture as required by the current guideline for the patient’s age and setting.

What antibiotic does IDSA recommend for confirmed or highly probable GAS?

IDSA first-line is penicillin V orally or amoxicillin for 10 days. Amoxicillin once or twice daily is preferred for better adherence. For penicillin allergy: azithromycin (if local susceptibility is confirmed) or a narrow-spectrum cephalosporin such as cephalexin. Clindamycin is an alternative for severe penicillin allergy.

Is this score validated for children under 3?

No. The Modified Centor (McIsaac) score is validated for patients aged 3 and older. Children under 3 rarely develop GAS pharyngitis; alternative clinical criteria apply in that age group.

Does this tool store patient data?

No. All calculations run entirely in your browser. Nothing is transmitted to any server, and no data is retained.

Modified Centor Score (McIsaac)

Enter age and four clinical findings to get the Modified Centor (McIsaac) score with a testing or antibiotic recommendation.

Clinical Criteria

Patient Age (McIsaac age modifier)

Clinical Findings (check all present)

Tonsillar exudate White or yellow patches on the tonsils +1 Tender anterior cervical lymphadenopathy Enlarged, tender nodes along anterior neck +1 Fever or history of fever Temperature >38 °C (100.4 °F) or reported fever +1 Absence of cough Check if patient does NOT have a cough +1

Result

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Modified Centor Score (−1 to 5)

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Criterion	Points
Total

For clinical decision support only. Always combine with full clinical assessment, local guidelines, and specialist judgment.

Summary

Enter age and four clinical findings to get the Modified Centor (McIsaac) score with a testing or antibiotic recommendation.

How it works

Select the patient age group — the McIsaac modification adds +1 for ages 3–14, 0 for 15–44, and −1 for 45 and older.
Check each of the four clinical findings present on examination or history.
The score totals automatically and maps to a GAS probability range (1–56%).
A color-coded result places the score in a pre-test probability band.
Apply current age-specific testing guidance before diagnosing GAS.

Use cases

Determine whether a rapid antigen detection test (RADT) or throat culture is warranted.
Support guideline-appropriate selection of GAS testing.
Reduce unnecessary antibiotic prescribing for viral pharyngitis.
Triage sore throat complaints in urgent care, telehealth, or primary care.
Educate trainees on structured pharyngitis risk stratification.
Document evidence-based clinical reasoning in patient encounter notes.

Frequently Asked Questions

Last updated: 2026-09-20 · Reviewed by Nham Vu