Carrier rates of group A streptococci in Australian wet tropics and their impact on the clinical usefulness of throat swabs

Abstract

Background and objectives: Rapid point-of-care tests (POCT) are likely to assist with the detection of group A streptococci (GAS), but their usefulness is determined by the presence of carriers of GAS. This is insufficiently explored in the wet tropics.

Method: This study included 77 patients attending primary care in the wet tropics complaining of a sore throat, and 49 healthy controls. Carrier rates of GAS and the positive and negative etiological predictive values (P-EPV and N-EPV, respectively) of a POCT were calculated.

Results: The carrier rates were 8.3% among healthy children and 2.7% for adults. The P-EPV for children was 71% (95% confidence interval [CI]: 0.0-100%) and for adults it was 85% (95% CI: 0.0-100%). The corresponding N-EPV was 99% (95% CI: 95-100%) for children and 99% (95% CI: 98-100%) for adults.

Discussion: N-EPV, ruling out GAS, was sufficiently high with narrow CIs to allow for defining a stopping rule to avoid unnecessary antibiotic prescribing.