Most sore throats are viral and clear on their own. But a small fraction are group A Streptococcus (strep throat) — and treating those matters, because untreated strep can lead to rare but serious complications like rheumatic fever. The challenge is that viral and bacterial sore throats feel nearly identical. The Centor criteria are the clinician's shortcut for deciding who actually needs a swab.
The Four Centor Points
Developed by Dr. Robert Centor in the 1980s and still used (with modifications) today, the score assigns one point for each of four findings. A higher score means a higher probability that the sore throat is strep:
- Tonsillar exudate — white or yellow patches on the tonsils
- Tender anterior cervical lymph nodes — swollen, painful glands in the neck
- Fever (history or measured) — a temperature above ~38°C / 100.4°F
- Absence of cough — strep typically does not come with a cough or runny nose
A modified version (the McIsaac score) also subtracts a point for patients over 44 and adds one for those 14 and under, since age shifts the base probability. This matters because most sore throats in adults are viral, while strep is more common in school-aged children.
What the Score Actually Means
Roughly speaking: with 0–1 Centor points, strep is unlikely (under ~10–20%) and a test is usually not warranted. With 2 points, testing is recommended. With 3–4 points, the pre-test probability is high enough that a rapid antigen test — or testing plus empiric treatment — is standard. This is exactly the guidance from the U.S. Centors for Disease Control and Prevention (CDC) and the Infectious Diseases Society of America (IDSA): don't treat on symptoms alone, confirm with a test.
Why Testing Still Matters
The danger of guessing is two-sided. Over-treating with antibiotics drives resistance and upsets the microbiome; under-treating genuine strep risks complications. A rapid strep test at the clinic catches the antigen directly, and when it's negative in a high-suspicion case, a throat culture or molecular test settles it. The takeaway: a sore throat with a cough and sniffles is almost certainly a cold — but fever, exudate, and neck glands without a cough are the red flags that earn you a swab.
When to Seek Care
Self-assessment is useful, but it is not a diagnosis. See a clinician if you have difficulty swallowing or breathing, a muffled voice, drooling, a fever above 39°C (102°F), symptoms lasting beyond a week, or a rash alongside the sore throat. These fall outside the ordinary viral throat and warrant prompt evaluation.