Calculators & Tools

Centor Score (McIsaac modified)

Likelihood of group A streptococcal pharyngitis.

1 What is the Centor Score (McIsaac modified)?

The Centor Score (McIsaac modified) is a infectious scoring tool used in paediatric practice. Likelihood of group A streptococcal pharyngitis. It scores 5 criteria and interprets the total across 3 bands, so the number always arrives with the severity it implies rather than on its own. In PediAid each criterion is shown as a labelled option with the weight it carries, so the total can be checked rather than taken on trust.

2 When to use it

  • Grading severity at the bedside in infectious
  • Recording an objective severity band in the case notes
  • Deciding when a total crosses the threshold for escalation
  • Re-scoring to track whether a child is improving or deteriorating
  • Checking the exact criteria of a score used infrequently

3 Formula & method

The score sums 5 criteria: Tonsillar exudate or swelling; Tender / swollen anterior cervical nodes; History of fever > 38 °C; Cough; Age. Totals are then banded: any score - Low risk: score ≤1 - roughly 1-10% risk of strep. No testing or antibiotics required; 2 points or more - Intermediate: score 2-3 - roughly 11-35% risk. Perform rapid antigen test or throat culture and treat if positive; 4 points or more - High risk: score ≥4 - roughly 50% risk. Test and treat if positive; empirical antibiotics considered in some settings.
  • The McIsaac modification adds the age adjustment (−1 point for age ≥45, not scored negatively here).
  • Source: McIsaac WJ et al. The validity of a sore throat score in family practice. CMAJ 2000;163:811-5.

4 Frequently asked questions

How many criteria does the Centor Score (McIsaac modified) use?

5. They are Tonsillar exudate or swelling; Tender / swollen anterior cervical nodes; History of fever > 38 °C; Cough; Age.

What do the bands of the Centor Score (McIsaac modified) mean?

The total is interpreted as: any score - Low risk: score ≤1 - roughly 1-10% risk of strep. No testing or antibiotics required; 2 points or more - Intermediate: score 2-3 - roughly 11-35% risk. Perform rapid antigen test or throat culture and treat if positive; 4 points or more - High risk: score ≥4 - roughly 50% risk. Test and treat if positive; empirical antibiotics considered in some settings.

Does the score replace clinical judgement?

No. It is a structured way to record and communicate severity. A clinician concerned about a child should act on that concern regardless of the total.

Where does this score come from?

The McIsaac modification adds the age adjustment (−1 point for age ≥45, not scored negatively here).

Does it work offline?

Yes. Score definitions are bundled with the PediAid app, so the score computes without a connection.

For qualified clinicians. This page and the PediAid app are a clinical aid only. Calculations and reference data must be verified against the patient's clinical context, the source guideline and your local protocols before any treatment decision is made.