Throat Infection Test
Note: this site is for informational purposes only. To view test results or book a test, use the NHS app in England or contact your GP.
A throat infection test detects bacteria or other microorganisms causing infection using a swab taken from the back of the throat. It is used to diagnose the cause of a sore throat—such as streptococcal infection—and to help guide appropriate antibiotic treatment.
Why get tested?
To diagnose a possible bacterial infection of the throat (usually Streptococcus pyogenes)
When to get tested?
If you have a sore throat and fever and your doctor thinks it may have a bacterial cause (although most sore throats are caused by viruses and won’t require antibiotics)
Sample required?
The bacteria are tested for by throat culture. Your doctor may use a tongue depressor to hold down your tongue, and then insert a special swab into your mouth and brush it against your throat and tonsils. The swab will be sent to a laboratory, where culture is performed.
Test preparation needed?
No test preparation is needed. The test should be performed before antibiotics are prescribed.
Common questions
The majority of sore throats are caused by a virus and do not require active treatment with antibiotics. Some, caused by the Streptococcus pyogenes bacterium, may be severe and are treatable with antibiotics. Your doctor will assess you based on your symptoms and may take a throat culture to help make the correct diagnosis if they think you might have a bacterial infection of your throat. This allows your doctor to prescribe the correct antibiotics for treatment. A throat culture may take several days to provide results.
Your doctor may request this test if you have a sore throat and a fever that might be due to a bacterial infection. Other symptoms include:
- tonsils that may appear red with white or yellow spots at the back of the throat
- a swollen, tender neck
- skin rash
- weakness
- loss of appetite, feeling sick
- flu-like illness, aching body
A positive throat culture indicates the presence of group A streptococci, the bacteria that cause sore throats.
A sore throat due to a bacterial infection may spread through person-to-person contact. Symptoms usually occur within two to seven days after exposure. If untreated, this throat infection can create serious lifelong problems in a small minority of patients, however these complications are very rare in the UK.
This infection is most common in 5- to 15-year-olds. Up to 20% of school children may be “carriers” – people who have the bacteria but who have no symptoms. Carriers can still spread the infection to others.
Five to 10 days depending on which antibiotic prescribed
Twenty-four hours after starting medication
Usually after one full day of therapy and absence of significant fever.
Other family members, including adults, can contract the bacteria. They must be vigilant and seek healthcare attention if feeling unwell.
Antistreptolysin O (ASO) titre is a blood test used to help diagnose a current or past infection with Group A strep (Streptococcus pyogenes). It detects antibodies to streptolysin O, one of the many streptococcus antigens. This test is rarely used now compared to thirty years ago. For an acute throat infection, this test is not performed; the throat culture is used. It is because ASO may take at least a week to become positive after the infection. However, if a doctor is trying to find out if someone had a recent infection that may not have been diagnosed, this test could be helpful. In addition, it may be used to help diagnose rheumatic fever, which occurs weeks after a bacterial throat infection when the throat culture would no longer be positive.