Centor Strep Score Calculator
Four signs plus age to strep score and band.
What it does
Sore throats are mostly viral, but a few hide strep that wants antibiotics. The Centor score sorts them with four signs plus age: fever, exudate, tender nodes, no cough. Points predict strep probability.
The tool above adds the present signs with McIsaac age adjustment and prints score, risk band, and action. Low scores rest at home; high scores see a clinician for testing and treatment.
Family-physician and infectious-disease guidelines use these same criteria with throat testing behind treatment decisions. Age matters because strep clusters in school years; absence of cough separates strep from viral patterns.
Screen here, diagnose there. Scores never replace exams or tests, and antibiotics never treat viruses. Treat positives, watch negatives, and return for breathing trouble or dehydration.
How to use
- Mark each of the four signs present.
- Pick the age group.
- Read the score out of 4-plus.
- Read the strep risk band.
- Follow the action: care or clinician.
- Test positives treat; negatives safety-net.
Formula
- signs
- Four clinical signs, 1 point each.
- age
- Plus 1 child 3-14, 0 adult 15-44, minus 1 older 45-plus.
Each sign counts 1 with age adjustment clamped at zero below. Bands follow published McIsaac post-test ranges. Scores screen and sort; throat exam plus testing diagnoses.
Worked example
Example: 4 signs, adult
Adult with all four Centor signs.
- Fever, exudate, nodes, no cough: 4 signs.
- Age 15 to 44 adds 0.
- Score totals 4 pts.
- Band reads about 51% or more.
- See a clinician; test and treat per guidelines.
Reference table
| Score | Strep risk | Move |
|---|---|---|
| 0 | About 1 to 2% | Home care |
| 1 | About 5 to 10% | Home care, watch |
| 2 | About 11 to 17% | Consider testing |
| 3 | About 28 to 35% | Test |
| 4 or more | About 51% or more | Test and treat per guidelines |
Limits
- Screening only. Exams and tests diagnose.
- Bands are published ranges, not certainties.
- Kids under 3 score differently; see a clinician.
- Antibiotics need prescriptions, not scores.
Common mistakes
- Treating viruses with antibiotics.
- Skipping backup culture on negatives.
- Ignoring age adjustment.
- Testing without clinical signs.
- Waiting out breathing trouble.
Try it yourself
Quick checks. Answers sit tucked under each question.
Fever only, adult?
Fever alone in an adult scores 1 pt: about 5 to 10%. Symptomatic care, retest if worsening.
No signs, older adult?
No signs at 45-plus scores 0 pts (clamped): about 1 to 2%. Symptomatic care.
Questions
What goes into the Centor score?
Fever, tonsillar exudate, tender neck nodes, and absence of cough, one point each, plus age: plus 1 for ages 3 to 14, 0 for 15 to 44, minus 1 past 45. Totals run 0 to 4-plus.
What do the scores mean?
Roughly 1 to 2 % at 0, 5 to 10 % at 1, 11 to 17 % at 2, 28 to 35 % at 3, and over half at 4 or more. Low scores watch and wait; high scores test and treat.
Do low scores need antibiotics?
No. Viruses dominate low scores, so antibiotics add harm without help. Guidelines reserve testing and treatment for higher scores with clinical judgment.
Rapid test or culture?
Rapid antigen plus backup culture per guidelines, because rapids miss some true cases. Treat positives, safety-net negatives that worsen.
Why does age adjust the score?
Age, because strep concentrates in school years and fades later. A child with 2 signs outranks an older adult with the same pair.
What helps while waiting?
Fever control, fluids, rest, and honey for cough in those over one year old. Return for breathing trouble, dehydration, or no improvement in days.