Centor Score Calculator

Centor Score Calculator. 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. Also try the find Letter Grade with Percentage to Letter Grade Converter.

Age Range (years) *

Age modifies the original Centor score per McIsaac.

Tonsillar Exudate or Swelling *

Presence of exudate or swelling on the tonsils.

Tender Anterior Cervical Lymphadenopathy *

Tenderness of the anterior cervical lymph nodes.

Temperature > 38°C (100.4°F) or History of Fever *

Measured fever or patient-reported history of fever.

Absence of Cough *

Absence of cough increases strep likelihood.

Results

Modified Centor Score

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Probability of Strep Pharyngitis

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Clinical Recommendation

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What is the Centor Score and who developed it?

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. See also our calculate Test Score.

What are the five criteria in the Modified Centor (McIsaac) Score?

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.

What does each score mean in terms of strep probability?

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).

When should antibiotics be prescribed based on the Centor Score?

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.

Can this calculator be used in children under 3 years old?

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.

Is the Centor Score a definitive diagnostic tool for strep throat?

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.

Why does absence of cough increase the Centor Score?

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.

What is the difference between the original Centor Score and the McIsaac modification?

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. You might also find our Standard Score (Z-Score) Calculator useful.