Infectious disease

Modified Centor Score (McIsaac)

The Centor score helps stratify adult and pediatric patients with sore throat for Group A Streptococcus testing and treatment. The modified (McIsaac) version adjusts for age and includes four clinical criteria.

Age (years)

Age adjustment: ≤ 14 (+1), 15–44 (0), ≥ 45 (−1).

History of fever ≥ 38°C (100.4°F)

Subjective or measured fever

Absence of cough

Patient denies cough

Tender anterior cervical lymphadenopathy

Swollen, tender anterior cervical nodes

Tonsillar swelling or exudate

Erythema, swelling, or white exudates on tonsils

Centor (McIsaac) score

Score 2

Test if feasible (RADT or culture). Consider watchful waiting; risk ~11–17%.

How to Use This Calculator

Evaluate Centor criteria

Assess fever, cough, cervical lymphadenopathy, and tonsillar exudate/swelling in patients with sore throat.

Adjust for age

Add 1 point for children ≤ 14 years, subtract 1 point for adults ≥ 45 years.

Use score to guide testing/treatment

Follow IDSA/AAP guidelines for RADT, throat culture, or empiric therapy based on risk stratification.

Formula

Modified Centor Score = (Fever) + (Absence of cough) + (Tender anterior cervical nodes) + (Tonsillar swelling/exudate) + Age modifier

Each clinical criterion scores 1 if present. Age modifier: ≤14 (+1), 15–44 (0), ≥45 (−1). Total range −1 to 5.

Estimated probabilities: 0–1 (5–10%), 2 (11–17%), 3 (28–35%), 4–5 (51–53%).

Full Description

The modified Centor (McIsaac) score predicts the likelihood of Group A Streptococcus (GAS) pharyngitis using symptom-based criteria and age. It supports antimicrobial stewardship by identifying patients who benefit from rapid testing or culture before antibiotics, thereby reducing unnecessary prescriptions.

Use the score alongside clinical judgment and local epidemiology. Always follow guideline recommendations on when to test, treat empirically, or refrain from antibiotics. Negative rapid tests in children should be backed up with culture per IDSA guidelines.

Frequently Asked Questions

Should adults with score 0–1 be tested?

Testing is generally unnecessary; focus on symptomatic treatment unless high-risk exposure or local outbreaks exist.

What about patients already on antibiotics?

Recent antibiotic use may alter clinical findings and culture sensitivity; interpret scores cautiously and consider alternative diagnoses.

Do results apply to viral pharyngitis?

The Centor score is specific to GAS risk. Viral symptoms (cough, rhinorrhea) lower the score via the cough criterion.

Can the score be negative?

Yes. Adults ≥45 years without any positive criteria score −1, indicating very low likelihood of GAS.