TestPack Strep A kit for the rapid detection of group A streptococci on 11,088 throat swabs in a clinical pathology laboratory.

Results obtained with Abbott Laboratories' TestPack Strep A, a rapid test kit to detect group A streptococcal antigen on throat swabs, were compared with the culture results. All tests were performed by American Society of Clinical Pathology-registered technologists in a large clinical laboratory. A total of 11,088 throat swabs were tested; 9,161 belonged to pediatric patients and 1,927 to adults. For TestPack Strep A, the study demonstrated a sensitivity value of 0.91 and a specificity value of 0.96; positive predictive value and negative predictive values were 0.82 and 0.98, respectively. These data indicate that even when performed by experienced technologists, in a laboratory setting, approximately 1 of 10 patients with group A streptococcal tonsillopharyngitis will be missed if physicians rely solely on this direct antigen test. A backup culture on all patients who are negative by a rapid antigen detection test is recommended.