RAPID DETECTION OF STREPTOCOCCUS-PYOGENES IN PEDIATRIC-PATIENT SPECIMENS BY DNA-PROBE

A chemiluminescent DNA probe test (Group A Streptococcus Direct Test; Gen-Probe, Inc., San Diego, Calif ) for rapid, direct detection of cRN A of Streptococcus pyogenes in throat swabs was compared with conventi onal culture and identification techniques. Throat swabs from 277 pati ents suspected of having streptococcal pharyngitis were examined. By D NA probe alone, 10 specimens were positive, 51 were positive by both a ssays, and 8 were positive by culture alone. Thus, DNA probe sensitivi ty, specificity, and positive and negative predictive values were 86, 95, 84, and 96%, respectively. Including an indeterminate category, se nsitivity, specificity, and positive and negative predictive values we re 89, 96, 86, and 97%, respectively. After discrepancy testing, these values for the raw data improved to 90, 98, 93, and 97%, respectively . None of the 24 specimens that grew non-S. pyogenes beta-hemolytic st reptococci in culture were positive by the DNA probe. Because mucoid S . pyogenes strains are more virulent than nonmucoid strains, 24 isolat es were retrospectively tested with the DNA probe to ensure that both types would be detected equally well. Isolates were examined in pure c ultures as well as mixed with representative normal oral flora. There was no statistical difference in detection of any of the four groups. Group A Streptococcus Direct Test is a rapid, sensitive, and specific test for S. pyogenes.