Rapid-antigen detection tests for group a streptococcal pharyngitis: revisiting false-positive results using polymerase chain reaction testing.

We investigated mechanisms of the false-positive test results on rapid-antigen detection test (RADT) for group A Streptococcal (GAS) pharyngitis. Most RADT false-positives (76%) were associated with polymerase chain reaction-positive GAS results, suggesting that RADT specificity could be considered close to 100%. Finding that 61% of GAS culture-negative but RADT-positive cases were positive on both GAS polymerase chain reaction and Staphylococcus aureus testing, we posit bacterial inhibition as causative.