Strep throat is a common condition caused by infection of the streptococcus bacteria, which affects the tonsils and back of the throat. Because the symptoms – including a sore, dry throat, inflamed tonsils, swollen glands, and even white patches on the back of the throat – can come with various other illnesses, a test is needed to diagnose it with certainty.
The antibiotics that treat strep throat will not work if the infection is viral, so if a doctor suspects strep, they will perform a throat culture or rapid strep test to confirm. In either case, a long cotton swab is swiped over the back of the throat and tonsils, taking care to avoid the cheeks and tongue, to collect a sample. This takes no more than a few seconds; the sample is then tested in a lab. A throat culture is more accurate, but it takes two to three days for the results to come back, whereas a rapid stress test may be preferred for speed (results come back in about fifteen minutes). If a throat culture is performed, the doctor may choose to begin treatment before the results come back, if you display enough definitive symptoms.
In some cases, both tests may be performed: for example, if the rapid strep test comes back negative but there’s enough reason to believe it might be a false negative, your doctor may order a throat culture to confirm. Why is it not enough to simply assume it’s not strep and stop treatment? Strep throat can cause other complications such as rheumatic fever if it’s severe enough and left untreated, especially in children. Prompt treatment with antibiotics also shortens the time in which you’re contagious to others.
There are limits to the tests for strep throat: for one thing, it won’t help diagnose other causes such as what type of viral infection may be responsible. For another, the tests can react to both living and dead streptococcus bacteria, which can cause a positive test result even if there’s no longer an active infection. Neither test isn’t 100% accurate and may result in false positives or false negatives, however, the benefits of taking them for diagnosis outweigh the potential for incorrect results – treating strep correctly is important, so talk to your doctor.