Evaluation of Detect-A-Strep and the Culturette Ten-Minute Strep ID kits for detection of group A streptococcal antigen in oropharyngeal swabs from children

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Abstract
The Detect-A-Strep kit (DAS) and the Culturette Brand 10-Minute Group A Strep ID kit (CBTMSI) were compared with a sensitive culture method for detection of group A streptococci in oropharyngeal swabs from children. Specimens from 953 children aged 4 mo.-18 yr were inoculated to selective blood agar plates containing sulfamethoxazole-trimethoprim. Culture plates were incubated anaerobically for the 1st overnight period and aerobically in the presence of 10% CO2 for the 2nd overnight period. The same specimens were tested within 24 h by DAS (phase 1) or CBTMSI (phase 2). Of 538 specimens tested by DAS and 415 specimens tested by CBTMSI 135 (25.1%) and 150 (36.1%), respectively, were culture positive. DAS detected 87 of 135 (64.4%) and CBTMSI detected 93 of 150 (62.0%) culture-positive specimens. The specificities of DAS and CBTMSI were 96.5 and 99.6%, respectively. The predictive values of positive and negative results were 86.1 and 89.0% for DAS and 98.9 and 82.2% for CBTMSI. Because a reliable distinction between infected patients and carrier state patients cannot be made, neither DAS nor CBTMSI is sufficiently sensitive to replace the culture method.