A rapid strep test may assist a clinician in deciding whether to prescribe an antibiotic to a person with pharyngitis, a common infection of the throat.

Since the major cause of bacterial pharyngitis is GAS, the presence of this organism in a person's throat may be seen as a necessary condition for prescribing antibiotics.

In addition to undesirable side-effects in individuals, inappropriate antibiotic use is thought to contribute to the development of drug-resistant strains of bacteria.

[2] Microbial culture from a throat swab is a reliable and affordable alternative to an RST which has high sensitivity and specificity.

In most RSTs, this mucus sample is then exposed to a reagent containing antibodies that will bind specifically to a GAS antigen.

It involves mixing the sample with labeled antibodies and then with a special substrate on a film which changes colour to signal the presence or absence of GAS antigen.

[2] Therefore, a negative result from such a test cannot be used to exclude GAS pharyngitis, a considerable disadvantage compared with microbial culture, which has a sensitivity of 90% to 95%.