Performance of a solid phase enzyme immunoassay for detection of group A streptococci in a pediatric office laboratory as refereed by a hospital laboratory.

We evaluated the performance of a new rapid solid phase enzyme immunoassay, SUDS Group A Strep (MUREX Corp., Norcross, GA) for the detection of Group A beta-hemolytic streptococci in a pediatric office practice. Duplicate throat swabs were obtained from 341 children with pharyngitis. One swab was used in the SUDS test and the other was cultured in the office laboratory. Office SUDS and culture (sheep blood agar plate, aerobic 24-hour incubation) were compared with culture using reference techniques (sheep blood agar plate, anaerobic 48-hour incubation) in a hospital laboratory. Compared with hospital laboratory culture, the sensitivity of office SUDS (73.8%) was superior to that of office culture (66.6%) at P = 0.05. Specificities were 93.1 and 98.6%, respectively; positive predictive values were 86.1 and 96.6%; and negative predictive values were 85.9 and 83.5%. The sensitivity and specificity of SUDS compared with office culture were 88.5 and 87.8%, respectively, but would have been 93 and 94% had hemolyzed media not been used on several occasions in the office culture procedure. We conclude that SUDS Group A Strep was significantly more sensitive than throat cultures as performed in a typical pediatric practice although the performance of office cultures could have been improved by standard quality control techniques.