Evaluation of the Directigen Group A Strep test kit.

The Directigen Group A Strep test kit (Hynson, Wescott, and Dunning, Baltimore, Md.) was tested for its ability to detect group A streptococci directly from 147 throat swabs. The results were compared with results from conventional culture and Lancefield serological grouping tests. The data showed that 121 of 124 culture-negative throat specimens were also Directigen negative (98%) and that 21 of 23 culture-positive specimens were Directigen positive (91%). If specimens that provided less than 10 colonies per plate of beta-hemolytic streptococci were eliminated, all of the culture-positive specimens were Directigen positive. Positive or negative results were available within 65 to 70 min of testing. The Directigen method is relatively simple to perform and easy to interpret and provides accurate assessment of the presence or absence of group A streptococci in throat swabs, with little or no cross-reactivity with other beta-hemolytic groups.