EVALUATION OF SUPRAPUBIC BLADDER ASPIRATION FOR DETECTION OF GROUP-B STREPTOCOCCAL ANTIGEN BY LATEX AGGLUTINATION IN NEONATAL URINE

Our objective was to determine whether urine collection by suprapubic bladder aspiration (SBA) improves the specificity of the group B strep tococcal (GBS) latex agglutination (LA) test by avoiding contamination of urine with GBS from perineal and rectal colonization that can resu lt in a positive LA test in an uninfected infant when the urine is col lected by bag. Part 1 consists of a retrospective review of the medica l records of 113 infants who had urine collected by SBA for GBS LA tes ting as part of evaluation for possible sepsis. The sensitivity and sp ecificity of the urine LA test was assessed by comparing it with blood culture results. In part 2, a prospective analysis was performed of 1 9 newborns who had rectal and vaginal/penile cultures as well as urine by SBA and bag for GBS cultures and LA. Results of LA testing on urin e collected by both of these methods were compared with results of uri ne, perineal, and rectal cultures. In the retrospective review of GBS LA testing performed on 113 consecutive urine specimens collected by S BA from neonates being evaluated for suspected sepsis, the sensitivity and specificity were 67% and 89%, respectively, when compared with bl ood culture results. Twelve infants who had a positive LA test result but a sterile blood culture (BC-, LA+) were compared with 95 infants w ith both blood cultures and urine LA tests negative for GBS (BC-, LA-) . BC-, LA+ infants were more likely than those with BC-, LA- to have a n immature to total neutrophil (I/T) ratio greater than or equal to 0. 16 at 12 and 24 hours (p=0.04 and 0.02, respectively). In the prospect ive study, we found that a positive GBS LA test can be due to perineal contamination and possibly to gastrointestinal absorption of GBS anti gen. No false positive LA test results occurred on urine obtained by S BA; however, use of this method failed to detect the one infant with G BS bacteremia. Because of suboptimal sensitivity and specificity, use of the GBS LA test on urine obtained either by SBA or bag cannot be re commended for diagnosis of early onset GBS disease.