Comparison of three major antigen detection methods for the diagnosis of Group B streptococcal sepsis in neonates

Abstract

Because of the difficulty encountered in diagnosing early onset Group B streptococcal disease (GBS) in neonates and because of the proliferation of tests to detect the antigen in urine, we made qualitative and quantitative comparisons among the three major, commercially available, antigen detection systems. The methods compared were Wellcogen latex agglutination, Phadebact coagglutination, and counterimmunoelectrophoresis (CIE). We tested urine, with or without serum, and tracheal or gastric aspirates from 176 neonates admitted to Columbus Children's Hospital, with suspected GBS disease. Wellcogen and Phadebact were equally sensitive indicators of neonatal GBS sepsis (100%) as compared to CIE which was only 30% sensitive. CIE, however, did not produce any false-positives (100% specificity) while Phadebact coagglutination and Wellcogen latex agglutination were approximately 98% specific. As a side bar to the main study, we also set out to determine whether tracheal or gastric aspirates would be consistent and convenient sources of antigen as compared to urine. Consequently we determined that neither aspirate is a good source of antigen as performed by our method.