Use of Copan Liquid Media Transport Swabs for the Gen-Probe Group A Streptococcus Direct Test

ABSTRACT
The Gen-Probe Group A Streptococcus Direct Test is used to detect the presence or absence of group A streptococci directly from pharyngeal specimens. The package insert for this assay includes a list of swabs which have been specifically qualified for use with this assay. Because this assay utilizes a specific relative light unit cutoff of 4500 to differentiate between positive and negative test results, it is important that the swab used to collect the patient specimen be qualified for use in the assay. The purpose of this study was to compare Copan Liquid Amies swabs and Copan Liquid Stuarts swabs with one of the currently qualified swabs, the Becton Dickinson Culturette swab, for use in the Group A Streptococcus Direct Test. Paired Culturette and Copan swabs were collected from patients and tested in the same batch run of the Group A Streptococcus Direct Test. To date, 380 Copan Amies (130 total positive results; prevalence 34.2%) and 318 Copan Stuarts (97 positive test results; prevalence 30.5%) have been tested in parallel with Culturette swabs. Discrepancies were resolved by culture of the pledgets. There were no significant differences between the sensitivities and specificities of the Culturette swab and either the Copan Amies or Copan Stuarts swabs; however, a trend towards significance (p=.034) favoring the Copan Amies swab was observed. We found the Copan swabs easier to use because, unlike the Culturette swabs, there is no ampule to crush. In addition, it was easier to wring out the Copan swabs than the Culturette swabs after the swabs were placed in the assay extraction buffer. In conclusion, both the Copan Liquid Amies and Liquid Stuarts swabs are acceptable alternatives to the currently qualified swabs for use in the Gen-Probe Group A Streptococcus Direct Test.