Sensitivity and specificity of rapid diagnostic tests for detection of group B streptococcal antigen in bacteremic neonates.

Latex particle agglutination (LPA) testing for antigen to group B streptococcus (GBS) has been useful in the diagnosis of GBS sepsis in newborns. However, recent reports have demonstrated that the sensitivity of LPA assays may be as low as 27 to 54%. The purposes of the present study were to directly compare the abilities of four urine antigen assays to detect GBS antigen with clinical urine samples from neonates with GBS bacteremia and to evaluate the effect of the urine concentration on the sensitivities and specificities of these assays. Urine samples were collected serially from neonates with blood cultures positive for GBS or on admission from healthy full-term infants. One milliliter of urine was removed, and the remainder was concentrated to a volume of 1 ml. Unconcentrated samples were serially diluted with normal saline and were assayed to determine the highest dilution which would produce a positive test result. The Wellcogen, Bactigen, and Directigen LPA tests and ICON immunoassay were directly compared by using concentrated and unconcentrated urine specimens and urine specimens with known titers. A total of 94 urine specimens, including 61 concentrated and 75 unconcentrated specimens, from bacteremic infants were available for sensitivity testing, and 220 urine specimens from uninfected infants were available for specificity testing. There were significant differences in sensitivity among the four assays when they were performed on concentrated urine specimens, as follows: Directigen, 98%; Bactigen, 92%; ICON, 89%; Wellcogen, 68%. When the assays were performed on unconcentrated urine specimens, the Directigen (84%) and Bactigen (76%) assays were each significantly more sensitive than the ICON (59%) or Wellcogen (43%) assay. All four assays were significantly more sensitive in detecting GBS antigen in concentrated than in unconcentrated urine. The Directigen assay detected antigen in higher dilutions (geometric mean titer, 1:5) than the ICON (1:3), Bactigen (1.2), or Wellcogen (1:1) assay. The specificity was 99.5% for all four assays when concentrated urine was used and for the Bactigen, Directigen, and ICON assays when unconcentrated urine was used; the Wellcogen assay was 100% specific when unconcentrated urine was used. We conclude that there are significant differences in sensitivity but not specificity among the commercially available assays for the detection of GBS antigenuria when concentrated and unconcentrated urine specimens are tested. These differences in sensitivity may affect the abilities of clinicians to accurately diagnose GBS sepsis before culture results are available.

Effect of maternal race on outcome of preterm infants in the military.

Previous studies suggest that low birth weight black infants have less morbidity and birth-weight-specific mortality during the perinatal period than low birth weight white infants. We studied the effect of maternal race on outcome in preterm infants born at a military hospital that offers free access to obstetric and neonatal care. Between January 1, 1986, and December 31, 1991, data were prospectively collected on all 667 infants delivered at Wilford Hall USAF Medical Center with an estimated gestational age of less than 35 weeks. Three hundred ninety-two white infants and 165 black infants were included in the data analysis. The mean (+/- SD) birth weight was 1701 +/- 65 g for white infants and 1462 +/- 66 g for black infants. The mean estimated gestational age was 31.0 +/- 3.2 weeks for white infants and 29.9 +/- 3.8 weeks for black infants. Preeclampsia was more frequent in black mothers than in white mothers for the entire study population (21% vs 14%), but the birth weight differential between races remained after correction for preeclampsia. There were no significant differences between races in stillbirths, gender, maternal age, maternal transfer status, number of prenatal visits, or percentages of mothers with small-for-gestational-age infants, multiple-gestation infants, prolonged rupture of membranes, or initial prenatal visit during the first trimester. Intraventricular hemorrhage was more frequent in white infants at 27 through 29 weeks estimated gestational age (50% vs 13%). There were no significant differences between the two groups in survival or in the occurrence of severe intraventricular hemorrhage or bronchopulmonary dysplasia.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the differential white blood cell count in screening for group B streptococcal sepsis.

We compared several previously defined scoring systems using white blood cell indices as part of a retrospective evaluation of infants with early onset Group B streptococcal (GBS) sepsis. Nineteen newborns were diagnosed with GBS sepsis between January, 1988, and April, 1990. Case controls (n = 33) were selected from patients admitted to the Neonatal Intensive Care Unit for suspected sepsis. Complete blood counts obtained at admission and between 12 and 24 hours of age were reviewed. There was a significant change in the ratio of immature to total neutrophils in the GBS group over time. Scoring systems for neonatal sepsis by Manroe et al., Rodwell et al. and Spector et al. had poor sensitivity, specificity, positive predictive value and negative predictive value when initial white blood cell count criteria were used, but scoring systems by Manroe and Rodwell were 100% sensitive and had 100% negative predictive value when applied to the repeat white blood cell count. We conclude that a single early complete blood count may not be an adequate screening tool for early onset GBS sepsis and should not be used to rule out infection. Optimal screening for GBS sepsis requires a repeat complete blood count within the first 24 hours of age.

Children's sex-related stereotyping of colors.

4 studies addressed children's sex-related stereotyping of colors. Study 1 examined preschoolers' awareness of color stereotypes. Children were presented with 6 toy animals, identical except for color, and were asked to identify the sex of each animal and to select a favorite. Both sex identifications and toy preferences were highly consistent with adult color stereotypes. Study 2 demonstrated that clothing color influences preschool, kindergarten, and first-grade children's impressions of other children whose sex is known. Studies 3 and 4 indicated that the effects of stereotyping based on color are modest in comparison to the effects of stereotyping based directly on sex. In addition, color stereotyping did not show the regular age-related increase that is characteristic of sex-role stereotyping.