Acute throat infections are among the most common infectious diseases presented to primary healthcare and A&E departments and are frequently misdiagnosed. They are responsible for 2 to 4% of all primary care visits. Viruses cause 85% to 95% of throat infections in adults and children younger than 5. For those aged 5 to 15, viruses cause about 70% of throat infections, with the other 30% due to bacterial infections, mostly group A β-hemolytic streptococcus (GAS), which can cause 0.5m deaths a year. There are challenges in diagnosing GAS because its signs and symptoms are often indistinguishable from viral and other causes of sore throat.
If a doctor intends to treat suspected GAS pharyngitis, it is generally recommended that laboratory confirmation of the presence of GAS be sought to limit unnecessary antibiotic prescription. The gold standard laboratory investigation is of a bacterial culture of a throat swab. However, this is expensive, and there is a relatively long lag time between the collection of the specimen and final microbiological diagnosis: so doctors tend not to it.
Rapid antigen diagnostic tests (RADTs) are an alternative to the gold standard laboratory test for GAS. However, widespread use of RADTs has been hindered by low sensitivity for most commonly used RADTs (immunoassays). Reviews of RADTs performance have identified significant variability in the diagnostic accuracy, especially sensitivity, between different test methodologies.