Novel, rapid optical immunoassay technique for detection of group A streptococci from pharyngeal specimens: comparison with standard culture methods

Abstract

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,

Evaluation of two rapid antigen assays, BioStar Strep A OIA and Pacific Biotech CARDS O.S., and culture for detection of group A streptococci in throat swabs

“…In the current study we did not observe the same sensitivities and specificities for OIA reported by Harbeck (3).…”

“…These patients would have been treated unnecessarily. And finally, the authors do not address why the TH in their hands was significantly less sensitive than in previous reports (2,3) and why their views are inconsistent with widely held views on enrichment broths (4,5). Treatment of patients with pharyngitis is based on the information available to the physician.…”

“…The rapid diagnosis of S. pyogenes from throat swabs is preferred by many physicians and patients and has recently become possible by virtue of immunoassays which identify group A streptococcal carbohydrate antigen (1,3,5,9) or DNA probe assays which detect unique nucleic acid sequences (4,7,8). A problem with conventional rapid immunoassays has been a lack of sensitivity compared with that of culture.…”

“…Both studies used TH as a culture method. Harbeck et al(3) used, in addition to TH, either a selective streptococcal agar culture incubated at 35°C in 5% CO2 for 48 h with confirmation of streptococci by Streptex latex agglutination or a Trypticase soy blood agar culture incubated at 35°C anaerobically for 48 h confirmed by using PathoDx Strep Typing Sera (Diagnostic Products Corp. Los Angeles, Calif.). In contrast, we used, in addition to TH, 5% SBA incubated at 35°C in ambient air for 48 h, with confirmation of group A streptococci by Streptex latex agglutination.…”

Evaluation of a new immunologic test kit for rapid detection of group A streptococci, the Abbott Testpack Strep A plus

“…In the literature, the specificities of rapid tests for the detection of group A beta-hemolytic streptococci (GAS) vary from 54 to 100%, whereas the sensitivities range from 44.9 to 98.9% (1)(2)(3)(4)(5)(6)(8)(9)(10). The new enzyme-linked immunosorbent assay Testpack Strep A Plus (TPSAP; Abbott Laboratories, North Chicago, Ill.) has, according to the manufacturer's data, a specificity of 94.4% and a sensitivity of 89.9%.…”