Modified Centor Score Calculator

Modified Centor (McIsaac) score for streptococcal pharyngitis probability.

For educational and clinical reference. Not a substitute for medical judgment. See the medical disclaimer.
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Interpretation
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References

  1. 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.
  2. 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.

What is Modified Centor Score?

The modified Centor (McIsaac) score is a clinical prediction rule that estimates the probability of group A streptococcal pharyngitis in patients presenting with a sore throat, guiding rational use of rapid antigen testing and antibiotics. The original Centor criteria were published in 1981 and modified by McIsaac et al. in 1998 to add age adjustment. One point each is awarded for tonsillar exudates, tender anterior cervical lymphadenopathy, fever >38°C, and absence of cough; ages 3–14 add one, 15–44 zero, and ≥45 subtract one. Scores of 0–1 do not require testing; 2–3 warrant rapid testing; 4–5 suggest empiric or test-then-treat antibiotics.

How to use

  1. Score each clinical feature and select the age category.
  2. The Centor score (−1 to 5) and strep probability update instantly.
  3. Use score 2–3 as the testing zone; avoid empiric antibiotics in 0–1.

Frequently asked questions

What is the modified (McIsaac) Centor score?

A 5-criterion score for the clinical probability of group A streptococcal pharyngitis, adding age strata to the original 4-item Centor.

When should a rapid test be performed?

Scores 2–3 are the sweet spot for testing. Scores 0–1 do not need testing or antibiotics. Scores 4–5 may justify empiric therapy in some guidelines.

Is empiric therapy ever appropriate?

IDSA recommends confirmatory testing for nearly all adults to avoid unnecessary antibiotic use. ESCMID allows empiric therapy at score 4–5 in some settings.

Why is age included?

GAS pharyngitis incidence varies by age: highest in 3–14 (+1), baseline in 15–44, lowest ≥ 45 (−1).

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