Why score a sore throat?
Most sore throats are caused by viruses and do not need antibiotics. Only about 5% to 15% of adult sore throats and 20% to 30% of children’s are due to group A Streptococcus. The Centor criteria, published in 1981, and the McIsaac modification from 1998 help decide who needs a test.
The criteria
| Criterion | Points |
|---|---|
| Temperature above 100.4 °F (38 °C) | +1 |
| Absence of cough | +1 |
| Tender, swollen front neck lymph nodes | +1 |
| Swollen tonsils or exudate | +1 |
| Age 3 to 14 | +1 |
| Age 15 to 44 | 0 |
| Age 45 or older | −1 |
Worked example
A 25-year-old has a fever of 101 °F, no cough and tender neck nodes, but no exudate:
- Fever +1, no cough +1, nodes +1, tonsils 0, age 0.
- McIsaac score = 3.
- Probability of strep ≈ 28% to 35%: a rapid antigen test is advised, and antibiotics are prescribed only if it is positive.
Score, probability and action
| Score | Probability of strep | Usual approach in adults |
|---|---|---|
| 0 or less | 1–2.5% | No test, no antibiotics |
| 1 | 5–10% | No test, no antibiotics |
| 2 | 11–17% | Rapid strep test |
| 3 | 28–35% | Rapid strep test |
| 4 or 5 | 51–53% | Rapid test or culture; treat if positive |
The Infectious Diseases Society of America (IDSA) recommends testing rather than treating on symptoms alone. In children, a negative rapid test is often confirmed with a throat culture because missed strep can lead to rheumatic fever.
Why test even with a high score?
Even with 4 or 5 points, about half of patients do not have strep. Treating everyone with a high score would give antibiotics to many people who do not need them, adding side effects and resistance without benefit.
Treatment and recovery
Confirmed strep throat is usually treated with penicillin or amoxicillin for 10 days. Pain relief with acetaminophen or ibuprofen, fluids and rest help whatever the cause. Children can return to school 12 hours after starting antibiotics if the fever is gone.
Red flags
Difficulty breathing, inability to swallow saliva, drooling, a muffled “hot potato” voice, a stiff neck or swelling on one side of the throat need urgent care.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.