Medical

Centor Criteria Calculator

Calculate the Centor score to estimate the probability of strep throat in patients with sore throat.

Age
Tonsillar exudates
Tender anterior cervical lymph nodes
Fever (history or presence)
Absence of cough
Centor score
0
Low risk — 1-10% probability of strep

Risk Classification

ScoreRiskRecommendation
-1 to 1Low riskNo testing or antibiotics recommended
2 to 3Intermediate riskConsider rapid strep test
4 to 5High riskConsider empiric antibiotics or rapid strep test

Note: The Centor criteria is a clinical prediction tool. Always use clinical judgment and consider local strep prevalence.

The Centor Criteria (also known as the Modified Centor Score or McIsaac Score) is a clinical prediction rule used to estimate the probability that pharyngitis (sore throat) is caused by Group A Streptococcus (GAS). It helps guide decisions about testing and antibiotic treatment.

What Are The Centor Criteria?

The score assesses five clinical findings:

  1. Tonsillar exudates — Pus or white spots on the tonsils (+1 point)
  2. Tender anterior cervical lymph nodes — Swollen, painful lymph nodes in the front of the neck (+1 point)
  3. History of fever — Temperature ≥100.4°F (38°C) (+1 point)
  4. Absence of cough — No cough present (+1 point)
  5. Age adjustment:
    • 3-14 years: +1 point
    • 15-44 years: 0 points
    • 45+ years: -1 point

Formula

Centor Score=Age points+Exudates+Lymph nodes+Fever+No cough\text{Centor Score} = \text{Age points} + \text{Exudates} + \text{Lymph nodes} + \text{Fever} + \text{No cough}

Score Interpretation

ScoreRisk LevelProbability of StrepRecommendation
0-1Low1-10%Symptomatic treatment only
2-3Intermediate11-35%Consider rapid strep test
4-5High36-65%Consider empiric treatment or testing

Clinical Implications

Low Score (0-1)

  • Strep throat is unlikely
  • Testing and antibiotics generally not recommended
  • Focus on symptomatic relief (pain relievers, fluids, rest)

Intermediate Score (2-3)

  • Strep throat is possible but not certain
  • Rapid strep test or throat culture recommended
  • Treat based on test results

High Score (4-5)

  • Strep throat is likely
  • Rapid strep test recommended
  • Empiric antibiotics may be considered, especially if testing unavailable

Why Age Matters

Strep throat is most common in children aged 3-14 years and less common in adults over 45. The age adjustment reflects these epidemiological differences.

Limitations

  • The score provides probability estimates, not definitive diagnoses
  • Other causes of pharyngitis (viral, other bacteria) are not ruled out
  • Local strep prevalence affects predictive values
  • Clinical judgment should always be applied

References

  1. Centor RM, et al. The diagnosis of strep throat in adults in the emergency room. Med Decis Making. 1981;1(3):239-46.

  2. McIsaac WJ, et al. A clinical score to reduce unnecessary antibiotic use in patients with sore throat. CMAJ. 1998;158(1):75-83.