Enter your patient's clinical findings — age range, tonsillar exudate, tender anterior cervical lymphadenopathy, fever history, and cough presence — to calculate the Modified Centor (McIsaac) Score for strep pharyngitis. You'll get the total score plus the estimated probability of streptococcal infection and a recommended clinical action.
Modified Centor Score
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Probability of Strep Pharyngitis
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Clinical Recommendation
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The Centor Score was originally developed by Dr. Robert Centor in 1981 to estimate the probability of group A streptococcal infection in adults presenting with sore throat. It was later modified by McIsaac in 1998 to include an age adjustment, improving its accuracy across pediatric and adult populations.
The five criteria are: (1) age range — +1 for ages 3–14, 0 for 15–44, −1 for ≥45; (2) presence of tonsillar exudate (+1); (3) tender anterior cervical lymphadenopathy (+1); (4) fever above 38°C or history of fever (+1); and (5) absence of cough (+1). Scores range from −1 to +5.
Scores ≤0 carry a 1–2.5% probability; a score of 1 gives 5–10%; score 2 gives 11–17%; score 3 gives 28–35%; and scores of 4–5 carry a 51–53% probability of streptococcal pharyngitis, based on McIsaac's empirical validation (JAMA 2004).
Generally, scores ≤1 do not warrant antibiotics or throat culture. A score of 2–3 suggests consideration of a rapid antigen test or throat culture before prescribing. A score of 4–5 may justify empirical antibiotic treatment, though clinical guidelines vary — always apply clinical judgment.
No. The Modified Centor Score is validated for patients aged 3 years and older. Strep pharyngitis is uncommon in children under 3, and different diagnostic approaches are recommended for that age group.
No. The Centor Score is a clinical decision aid to estimate the probability of strep infection and guide testing or treatment decisions. It does not replace a rapid strep antigen test or throat culture for definitive diagnosis.
Cough is a typical symptom of viral upper respiratory infections, not bacterial pharyngitis. When cough is absent, a bacterial (streptococcal) cause becomes more likely, so the absence of cough adds one point to the score.
The original Centor Score used four criteria (exudate, lymphadenopathy, fever, absence of cough) and was designed for adults only. McIsaac added an age adjustment (+1 for ages 3–14, −1 for ≥45) to extend the tool's validity to pediatric patients and improve specificity in older adults.