Centor / McIsaac Score for Strep Pharyngitis
Predicts likelihood of Group A Streptococcal (GAS) pharyngitis to guide antibiotic prescribing. McIsaac modification adds age adjustment.
Score interpretation
McIsaac score ≤ 1: probability of group A streptococcus (GAS) about 10% or less (McIsaac 2004).
→ No throat swab and no antibiotic. Symptomatic treatment: regular analgesia (paracetamol / ibuprofen), adequate fluid intake. Safety-net advice (NICE NG84).
McIsaac score 2–3: probability of GAS about 11–35%.
→ Throat swab or rapid antigen test and treat only if positive; where testing is not used, no antibiotic or a back-up prescription (NICE NG84). Safety net.
McIsaac score 4–5: probability of GAS about 51–53%.
→ Treat empirically or test and treat (McIsaac 2004; NICE NG84: consider an immediate or back-up antibiotic). Adults: Phenoxymethylpenicillin 500mg QDS × 10 days (first-line). Amoxicillin 500mg TDS × 10 days (alternative — do NOT use if EBV/glandular fever suspected). Allergy: clarithromycin 250mg BD × 5 days. Advise on completing course. Children: use a children's formulary.
Interpretation bands for the Centor Score. Apply clinical judgement and local guidance.
References
- Centor RM, Witherspoon JM, Dalton HP, Brody CE, Link K. The diagnosis of strep throat in adults in the emergency room. Med Decis Making. 1981;1(3):239-246.
- McIsaac WJ, White D, Tannenbaum D, Low DE. A clinical score to reduce unnecessary antibiotic use in patients with sore throat. CMAJ. 1998;158(1):75-83.
- McIsaac WJ, Kellner JD, Aufricht P, Vanjaka A, Low DE. Empirical validation of guidelines for the management of pharyngitis in children and adults. JAMA. 2004;291(13):1587-1595.
- NICE NG84. Sore throat (acute): antimicrobial prescribing. 2018.
Related
Curated clinical cross-links plus same-class fallbacks.
- Phenoxymethylpenicillin (Penicillin V) · Antibiotic — Tonsillitis / Pharyngitis
- Doxycycline 100mg (Acne / Rosacea) · Oral tetracycline antibiotic (anti-acne / anti-rosacea)
- Lymecycline 408mg (Acne) · Oral tetracycline antibiotic (anti-acne)
- Erythromycin 2% Topical · Topical macrolide antibiotic (anti-acne)
- Mupirocin 2% Ointment · Topical antibiotic (pseudomonic acid)
- Fusidic Acid 2% Cream · Topical antibiotic (steroidal antibiotic)
- Adult Upper Airway Obstruction (Stridor) · DAS 2015 unanticipated difficult airway; RCEM
- Epistaxis Management · ENT-UK / NICE
- Acute Otitis Media · NICE NG91 2018
- Tonsillitis and Sore Throat · NICE NG84 2018
- Benign Paroxysmal Positional Vertigo · NICE CG124 / AAO-HNS Guidelines
- Acute Rhinosinusitis · NICE NG79 2017 / EPOS 2020
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.