Optical Immunoassay Test for Group A β-Hemolytic Streptococcal Pharyngitis

Abstract

To compare the accuracy of an optical immunoassay (OIA) for the rapid diagnosis of group A streptococcal pharyngitis with blood agar plate (BAP) culture. Blinded comparison with criterion standard. A total of 6 private pediatricians' offices, 3 in Connecticut and 3 in Chicago, III. A total of 2113 consecutive patients with acute pharyngitis, 983 in Connecticut and 1130 in Chicago. The sensitivities and specificities of OIA and BAP culture (both performed and interpreted in the office) were determined using a research laboratory's interpretation of a combination of BAP culture and Todd-Hewitt broth (THB) culture of transport tube pledget as criterion standard. Among patients in Connecticut, the sensitivities of the OIA and BAP culture were 94% and 89%, respectively (P=.004), while the specificities were 96% and 99%, respectively (P=.001). Among patients in Chicago, the sensitivities of the OIA and BAP culture were 79% and 72%, respectively (P<.001), while the specificities were 89% and 99%, respectively (P<.001). In each of the 6 pediatricians' offices, the OIA was more sensitive than the BAP culture. Combining the data from Connecticut and Chicago, the overall sensitivities of the OIA and BAP culture were 84% and 78%, respectively (P<.001), while the specificities were 93% and 99%, respectively (P<.001). The results of this comprehensive office-based investigation suggest that with adequately trained personnel, negative OIA test results may not always need to be routinely confirmed with BAP cultures.