SUPERIORITY OF CONVENTIONAL CULTURE TECHNIQUE OVER RAPID DETECTION OFGROUP-A STREPTOCOCCUS BY OPTICAL IMMUNOASSAY

An optical immunoassay (OIA) has been reported to be more sensitive th an conventional culture for the detection of Group A Streptococcus, el iminating the need for culture. We attempted to confirm the sensitivit y and specificity through a laboratory quantitation study and a clinic al trial. OIA did not detect Group A Streptococcus below 10(5) colony forming units (CFU). Culture detected Streptococcus to 10(2) CFU from the inoculated swab. In the clinical study, throat swabs were obtained from 77 patients in an outpatient clinic. Compared with culture, the sensitivity of OIA was 78% and the specificity was 90%. These results demonstrate that OIA was less sensitive than culture in seeded experim ents and missed 22% of positives in clinical practice. Our study, cont rary to previous reports, suggests that OIA is nor sensitive enough to be used as the sole assay for Group A Streptococcus pharyngitis.