McIsaac Score

McIsaac Score: Modified Centor Criteria. Incorporates age to improve diagnostic specificity for Group A Strep (GAS).

Clinical Criteria

Patient Age

Guidelines & Evidence

Clinical Details

Section 1

When to Use

Assessment of patients (children and adults) presenting with sore throat

Screening for Group A Streptococcus (GAS) pharyngitis

Determining the need for Rapid Antigen Detection Test (RADT) or culture

Guiding antibiotic stewardship in primary care and emergency settings

Section 2

Formula & Logic

Scoring Criteria

Temperature > 38°C (100.4°F) (1 pt)

Absence of cough (1 pt)

Swollen, tender anterior cervical nodes (1 pt)

Tonsillar swelling or exudate (1 pt)

Age: 3–14 years (+1 pt) | 15–44 years (0 pt) | ≥45 years (-1 pt)

Management Recommendations

≤ 1 points	No further testing or antibiotics needed (~5-10% risk).
2–3 points	Perform RADT/Culture; treat only if positive (~10-30% risk).
≥ 4 points	Empiric antibiotics or RADT/Culture (~51% risk).

Section 3

Evidence Appraisal

Validation

A clinical score to reduce unnecessary antibiotic use in patients with sore throat.

McIsaac WJ et al. • CMAJ.. 1998;158(1):75-83. Showed significant reduction in antibiotic prescribing when using the age-adjusted score.

Last Comprehensive Review: 2026

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