Comparison of direct specimen testing utilizing TestPack strep A with testing of specimens following a two-hour broth enrichment.
In a previous study, we demonstrated that a 2-h enrichment of throat swabs in broth followed by a direct fluorescent antibody test was significantly more sensitive than the Abbott TestPack Strep A for the detection of group-A streptococci. In this study, in an effort to simplify the technique, we utilized broth enrichment with an enzyme immunoassay detection method. A total of 1017 pharyngeal specimens were tested with TestPack Strep A (DTP), culture on a selective streptococcal agar, and a 2-h broth enrichment in Todd-Hewitt broth (THB) followed by TestPack Strep A (ETP). Subculture of the THB was used to arbitrate discordant test results. The sensitivities and specificities respectively were as follows: DTP (69% and 99%), ETP (90% and 98%), and SSA (97% and 100%). This enrichment method offers significantly greater sensitivity than direct testing for antigen yet still allows the potential for finalized same-day reporting of results.
Bourbeau
P P
PP
Department of Laboratory Medicine, Geisinger Medical Center, Danville, Pennsylvania 17822.
Heiter
B J
BJ
Anhalt
J P
JP
Naumovitz
D W
DW
D003470:Culture Media; D005188:False Negative Reactions; D005189:False Positive Reactions; D006801:Humans; D007124:Immunoenzyme Techniques; D010612:Pharyngitis / Q000175:diagnosis*; D010614:Pharynx / Q000382:microbiology*; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis*; D013297:Streptococcus pyogenes / Q000302:isolation & purification*
D003470:Culture Media