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

Abstract

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. This study included 77 patients attendingprimary care in the wet tropics complaining of a sore throat, and 49healthy controls. Carrier rates of GAS and the positive and negative etiological predictive values (P-EPV and N-EPV, respectively) of a POCT were calculated. The carrier rates were 8.3% among healthy children and 2.7% for adults. TheP-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 was99% (95% CI: 95-100%) for children and99% (95% CI: 98-100%) for adults. N-EPV, ruling out GAS, was sufficiently high with narrow CIs to allow for defining a stopping rule to avoid unnecessary antibiotic prescribing.