Rapid Strep Test
Also written as: Rapid antigen detection test, RADT, Strep A swab
A throat swab that looks for group A strep bacteria, with a result in minutes.
What it measures
It detects antigens - surface proteins - of group A streptococcus bacteria on a throat swab. It looks for the presence of the bacteria itself, not the body's response to it, and delivers a result in roughly five to ten minutes.
Why a doctor orders it
It is used when a sore throat is being evaluated and knowing whether group A strep is present would change what happens next. Most sore throats are viral, and the test is the quick way to sort the bacterial minority from the rest during the visit.
What is generally associated with a higher result
A positive result generally indicates that group A strep bacteria are present in the throat, and false positives are uncommon. The test cannot distinguish an active infection from carriage - some people, children especially, carry the bacteria without it being the cause of their current symptoms.
What is generally associated with a lower result
A negative result generally makes strep less likely but does not fully rule it out, because rapid tests miss a portion of true cases. In children and adolescents, a negative rapid test is often backed up with a throat culture, which takes a day or two but catches what the rapid test missed.
Everyday things that move this number
Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:
- Swab technique - a good sample rubs both tonsils and the back of the throat
- Recent antibiotics, which can turn the test negative
- How early or late in the illness the swab is taken
- Eating, drinking, or using mouthwash immediately before the swab
Questions to take to your appointment
- If this is negative, will a culture be sent as a backup?
- Could a virus be causing the symptoms even with a positive result?
- Does anyone else in the household need to be checked?
Build a printable questionnaire with your own results →
Where to read more
MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .
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