How is the Centor / McIsaac score calculated?

Add a point for tonsillar exudate, tender anterior cervical nodes, fever above 38°C, and the absence of cough, and adjust for age (+1 for 3–14 years, 0 for 15–44, −1 for 45 and over). The McIsaac modification is the age adjustment.

What does the score tell me?

It estimates the likelihood that the sore throat is Group A streptococcal — for example, roughly 8% at 0 rising to about 55% at 4 (ages 3+). It is a likelihood, not a diagnosis.

Does the score tell me whether to test or prescribe antibiotics?

No. The CDC/ACP/IDSA test-or-treat thresholds are shown only as an attributed note. The decision is the clinician’s, guidelines differ, and the tool never names or doses an antibiotic.

Is it reliable in Indian practice?

Use clinical judgement: rapid antigen tests and throat culture are often unavailable or costly in low-resource settings, and testing and treatment thresholds differ between guidelines. The score supports, it does not replace, assessment.

Does any of the data I enter leave my browser?

No. The scoring runs entirely in your browser; nothing you enter is sent to a server or stored. The print option produces a clean worksheet you can save as a PDF.

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Centor / McIsaac score calculator

Score the modified Centor (McIsaac) criteria for a sore throat — age, tonsillar exudate, tender anterior nodes, fever, and absence of cough — for the published likelihood of Group A streptococcus. A screening aid, not a diagnosis — and nothing you enter leaves your device.

For a patient with a sore throat, set the age band and tick each criterion that is present. Each criterion scores 1 point; age adjusts the total by +1 (3–14y), 0 (15–44y), or −1 (≥45y).

Age band

Criteria present

Tonsillar exudate or swellingExudate on, or swelling of, the tonsils+1Tender / swollen anterior cervical nodesTender or enlarged anterior cervical lymph nodes+1Temperature > 38 °C / history of feverMeasured temperature above 38 °C, or a reported fever+1Absence of coughCough is absent (a cough that is present scores 0)+1

Centor / McIsaac total

0/ 5

Lower likelihood descriptor

Published GAS likelihood (ages 3+)8%

Rapid antigen tests and throat culture are often unavailable or costly in low-resource settings, so what testing is available locally shapes how the score is used. Read the percentage as a population estimate for the score, not this patient's guaranteed likelihood of strep.

Not a test-or-treat decision

What guidelines do with this number is a separate, clinical decision. The published rules have historically used the score to frame whether testing for GAS is worthwhile (broadly: no testing at low scores, rapid antigen test or culture at intermediate scores), but those test-or-treat thresholds differ between IDSA, CDC/ACP, NICE, and Indian practice and change over time. This tool does not recommend testing, and never names or doses an antibiotic — the decision rests with the treating clinician.

Screening aid, not a diagnosis. This estimates the likelihood that a sore throat is caused by Group A streptococcus from a published, validated prediction rule (Fine, Nizet & Mandl, Arch Intern Med 2012; n=206,870). It does NOT diagnose strep and does NOT recommend testing, antibiotics, a drug, a dose, or a duration. The decision to test or treat is the clinician's, and testing and treatment thresholds differ between IDSA, CDC/ACP, NICE, and Indian practice and change over time. Rapid antigen tests and culture are often unavailable or costly in low-resource settings. Scores support, not replace, clinical assessment.

Privacy: Runs entirely in your browser — nothing you enter is sent to a server or stored.

Criteria, point values, and the per-score GAS-likelihood percentages reproduced from: Fine AM, Nizet V, Mandl KD. Large-Scale Validation of the Centor and McIsaac Scores to Predict Group A Streptococcal Pharyngitis. Arch Intern Med 2012;172(11):847–852 (PMC3627733)..

How the Centor / McIsaac score works

The modified Centor (McIsaac) score adds points for age, tonsillar exudate, tender anterior cervical nodes, fever, and the absence of cough to estimate how likely a sore throat is to be Group A streptococcus. A higher score means a higher likelihood — for example, around 1 in 2 at a score of 4. The score frames whether testing is worthwhile; it does not diagnose strep or, by itself, prescribe antibiotics, and the test-or-treat threshold differs by guideline and by what testing is available locally.

Many teams still tally the criteria on a scrap of paper. If you run an ENT clinic workflow on Avinya Plus, the same arithmetic can live on the note: build the Centor criteria into an ENT or GP template and total them with the formula engine, so the likelihood sits beside the examination instead of on a calculator. The arithmetic is the engine's; the test-or-treat decision stays yours.

Frequently asked questions

How is the Centor / McIsaac score calculated?: Add a point for tonsillar exudate, tender anterior cervical nodes, fever above 38°C, and the absence of cough, and adjust for age (+1 for 3–14 years, 0 for 15–44, −1 for 45 and over). The McIsaac modification is the age adjustment.
What does the score tell me?: It estimates the likelihood that the sore throat is Group A streptococcal — for example, roughly 8% at 0 rising to about 55% at 4 (ages 3+). It is a likelihood, not a diagnosis.
Does the score tell me whether to test or prescribe antibiotics?: No. The CDC/ACP/IDSA test-or-treat thresholds are shown only as an attributed note. The decision is the clinician’s, guidelines differ, and the tool never names or doses an antibiotic.
Is it reliable in Indian practice?: Use clinical judgement: rapid antigen tests and throat culture are often unavailable or costly in low-resource settings, and testing and treatment thresholds differ between guidelines. The score supports, it does not replace, assessment.
Does any of the data I enter leave my browser?: No. The scoring runs entirely in your browser; nothing you enter is sent to a server or stored. The print option produces a clean worksheet you can save as a PDF.

Sources

Fine AM, Nizet V, Mandl KD. Large-Scale Validation of the Centor and McIsaac Scores to Predict Group A Streptococcal Pharyngitis. Arch Intern Med 2012;172(11):847–852 (PMC3627733).

The criteria and the per-score GAS-likelihood percentages are reproduced from Fine, Nizet & Mandl, Arch Intern Med 2012 (PMC3627733). The associated test/treat thresholds vary by guideline (IDSA, CDC/ACP, NICE, Indian practice) and are shown only as an attributed note. Reviewed against the source on 2026-06-29.

Keep the score on the consultation note.

In Avinya Plus you can build the Centor criteria into an ENT or GP template, total them automatically, and keep the likelihood on the record — the test-or-treat decision stays with you. See it on a quick demo.