Comparison of TestPack Plus Strep A with selective and nonselective culture media for detection of group-A streptococci.
The TestPack Plus Strep A (TPPSA), an immunoassay method, was compared with conventional culture methods including nonselective trypticase soy agar with 5% sheep blood and selective SXT blood agar for detection of group-A streptococci (GAS). A total of 452 throat swabs was evaluated, of which 261 (57.7%) and 191 (42.3%) were compared with culture using nonselective and selective media, respectively. Of 261 specimens evaluated on nonselective media, 71 (27.1%) were culture positive for GAS. TPPSA demonstrated a sensitivity of 91.6% and a specificity of 94.2% with positive and negative predictive values of 85.5% and 96.8%, respectively. Of 191 specimens evaluated on selective media, 44 (23.0%) were culture positive for GAS. TPPSA demonstrated a sensitivity of 93.2% and a specificity of 98.0% with positive and negative predictive values of 93.2% and 98.0%, respectively. The performance of TPPSA when compared with nonselective and selective media demonstrated a similar sensitivity, but a higher specificity was seen when compared to selective media. Overall, TPPSA was extremely easy to perform, had built-in procedural controls, required minimal technologist time, and was easy to interpret. With an accuracy of 93.5% when compared with nonselective media and 96.9% when compared with selective media, TPPSA could be recommended as a reliable method for detection of GAS.
Schwabe
L D
LD
Department of Pathology, Evanston Hospital, Illinois 60201.
Gobbo
A F
AF
Gottschall
R L
RL
Randall
E L
EL
D000942:Antigens, Bacterial / Q000032:analysis*; D015169:Colony Count, Microbial; D003470:Culture Media; D006801:Humans; D007118:Immunoassay; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic; D012141:Respiratory Tract Infections / Q000175:diagnosis; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis*; D013297:Streptococcus pyogenes / Q000276:immunology / Q000302:isolation & purification*
D000942:Antigens, Bacterial; D003470:Culture Media; D011933:Reagent Kits, Diagnostic