Novel, rapid optical immunoassay technique for detection of group A streptococci from pharyngeal specimens: comparison with standard culture methods.
A novel immunoassay system based on the changes in the reflection of light, termed an optical immunoassay (OIA), was utilized to directly detect group A streptococcal (GAS) carbohydrate antigen from clinical specimens. In two studies, a total of 1,275 throat swabs were tested for the presence of this antigen with the Strep A OIA rapid detection system and the results were compared with those of standard culture methods. In both studies, the Strep A OIA yielded more positive results than plating of the throat swab onto a selective agar, Trypticase soy agar containing sheep blood, or an enriched broth. In one study, the sensitivity and specificity of Strep A OIA compared with those of the broth-enriched culture were 97.4 and 95.6%, respectively. In a second study a sensitivity of 98.9% and a specificity of 98.6% were achieved. It was also shown that the carbohydrate antigen could be detected in the absence of viable GAS organisms. The Strep A OIA is an easily interpretable method and was shown to be more sensitive than routine culture methods for detecting GAS infections directly from throat swabs.
Harbeck
R J
RJ
National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
Teague
J
J
Crossen
G R
GR
Maul
D M
DM
Childers
P L
PL
D000942:Antigens, Bacterial / Q000032:analysis; D001431:Bacteriological Techniques; D003470:Culture Media; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D010612:Pharyngitis / Q000175:diagnosis / Q000382:microbiology; D010614:Pharynx / Q000382:microbiology*; D013290:Streptococcal Infections / Q000175:diagnosis / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000276:immunology / Q000302:isolation & purification*
D000942:Antigens, Bacterial; D003470:Culture Media