Methods for the Rapid Screening of Group A Streptococci: Fluorescent in situ Hybridization versus Immunochromatography

Objective: To evaluate the accuracy of detection for screening group A streptococci (GAS) in pediatric clinics using fluorescent in situ hybridization (FISH) and immunochromatographic assay (ICA). Subjects and Methods: A group of 630 children who attended an outpatient clinic with signs and symptoms of acute upper respiratory tract infection were enrolled in this study. Specimens were collected using a double-swab collection device. Culturing methods were employed as the gold standard for comparison. Discordant results (i.e., positive results for FISH or ICA along with negative culture results) were further evaluated by using Todd-Hewitt broth (THB) with subsequent subculture for group A selective streptococcus agar. True-positive or false-positive of GAS was determined by the presence or absence of THB subculture. The diagnostic characteristics of FISH and ICA were assessed. Results: After discrepant analysis, the sensitivity, specificity and positive and negative predictive values were as follows: 89.2, 100, 100 and 95.4%, respectively, for FISH; corresponding values for ICA were 76.8, 98.6, 96.1 and 90.5%. Conclusion: The results demonstrated that the FISH assay had a higher detection sensitivity than ICA and is suitable for rapid and accurate GAS screening in pediatric clinics.