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Centor / McIsaac Score — Strep Pharyngitis

Predicts the probability of Group A streptococcal (GAS) pharyngitis in adults and children ≥ 3 years, with testing and antibiotic guidance. Calculations run locally in your browser.

Age

McIsaac modification: +1 if 3–14 years, 0 if 15–44, −1 if ≥ 45. Not validated under 3 years (viral causes predominate).

years

Enter age to set the age modifier.

Fever > 38°C (100.4°F)

By history in the past 24 hours OR measured in clinic. Touch-only assessment is not sufficient.

Absence of cough

Cough strongly suggests a viral upper respiratory infection. Lack of cough scores +1.

Tender anterior cervical lymphadenopathy

Palpable, tender anterior cervical nodes — not just any neck lymphadenopathy.

Tonsillar swelling or exudate

Tonsillar enlargement and/or white/yellow exudate on examination.

Centor / McIsaac Score

Disclaimer: This calculator supports clinical decision-making and is not a substitute for clinical judgment. The score is not validated in children < 3 years (viral aetiologies predominate and acute rheumatic fever risk is very low). Consider local epidemiology, ICMR / NCDC antimicrobial stewardship guidance, drug allergies, and red-flag features (drooling, stridor, trismus, unilateral neck swelling, asymmetric tonsils, immunocompromise) before prescribing. Penicillin V or amoxicillin remains first-line for confirmed GAS in India unless contraindicated.

References

  1. McIsaac WJ, Goel V, To T, Low DE. The validity of a sore throat score in family practice. CMAJ 2000;163(7):811–815.
  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.
  3. Shulman ST, Bisno AL, Clegg HW, et al. Clinical practice guideline for the diagnosis and management of group A streptococcal pharyngitis: 2012 update by the Infectious Diseases Society of America. Clin Infect Dis 2012;55(10):e86–e102.
  4. Indian Council of Medical Research. Treatment Guidelines for Antimicrobial Use in Common Syndromes (latest edition). New Delhi: ICMR.
  5. Indian Academy of Pediatrics. IAP Standard Treatment Guidelines — Acute Pharyngitis.

Probability bands follow McIsaac 2000 and IDSA 2012. Empirical antibiotic decisions should follow your local antimicrobial stewardship policy and ICMR guidance.

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