Outpatient evaluation of a rapid, direct test for detection of group A streptococci in throat swabs.
A latex agglutination test (Marion Laboratories) was compared with standard culture methods for the detection of Group A streptococci in two studies of 500 throat swabs each. Swabs were first inoculated to sheep blood agar and then tested for Group A streptococcal antigen. The direct test performed with nearly identical sensitivity and specificity in the two phases of the study. Overall, Group A streptococci were isolated from 91 specimens, and 81 (89%) of these were detected by the direct latex test. The predictive value positive for the latex test was 90%, and the accuracy was 98%. The sensitivity of the latex test for detection of specimens having ten or more colonies of Group A streptococci was 95%. Non-Group A beta-hemolytic streptococci were isolated from 65 specimens, and all of these specimens had negative latex tests. The authors' findings suggest that this direct latex agglutination test is a reliable screening method for rapid detection of Group A streptococci in outpatient throat specimens.
D000553:Ambulatory Care; D001431:Bacteriological Techniques; D003429:Cross Reactions; D006801:Humans; D007841:Latex Fixation Tests / Q000379:methods*; D010614:Pharynx / Q000382:microbiology*; D011237:Predictive Value of Tests; D013291:Streptococcus / Q000276:immunology; D013297:Streptococcus pyogenes / Q000302:isolation & purification*