Maternal serum screening for Down syndrome in the United States: a 1995 survey.

OBJECTIVE: Our goal was to determine the status of prenatal Down syndrome screening in the United States in 1995. STUDY DESIGN: Information was sought via questionnaire from laboratories participating in external proficiency testing. RESULTS: Services were provided to 2,498,000 women annually by 265 screening laboratories. All but 10 laboratories offered both open neural tube defect and Down syndrome screening. Twenty-one percent of Down syndrome interpretations were based on alpha-fetoprotein measurements alone; 79% also included other serum analytes. Sixty-six laboratories (26%) offered interpretations at 14 weeks' gestation or earlier. CONCLUSIONS: Some laboratories extend serum screening too early in gestation for optimal neural tube defect interpretation. When 1995 was compared with 1992, more women were being screened, a higher proportion were receiving a Down syndrome interpretation, and more interpretations were based on multiple analytes. Laboratories should be encouraged to use some combination of multiple markers when screening for Down syndrome.

Molecular relatedness of Staphylococcus epidermidis isolates obtained during a platelet transfusion-associated episode of sepsis.

Staphylococcus epidermidis was isolated from the blood of a 25-year-old pregnant woman following the administration of eight units of platelets. She had developed chills and a fever of 41.4 degrees C soon after the transfusions were completed. S. epidermidis was also obtained from all eight platelet units, as well as from the packed-erythrocyte unit associated with the first unit of platelets. The isolation of the same organism from these epidemiologically related sources provided us with the opportunity to phenotypically and genetically characterize the isolates. Several typing methods, including four molecular techniques, were used to increase our chances of finding any differences between the isolates under investigation. Phenotypic analyses demonstrated that S. epidermidis isolates from the patient, platelet units, and erythrocyte unit reacted in exactly the same manner in 15 biochemical tests, exhibited slime production, and had the same antibiotic susceptibility pattern. Genetic analyses, which included plasmid profiles, plasmid cross-hybridization, field inversion gel electrophoresis, and ribotyping, substantiated the relationships between the S. epidermidis isolates from the patient, platelet units, and erythrocyte unit. Eight S. epidermidis control strains unrelated to the case were found to differ significantly from the platelet-related strain.

Laboratory evaluation of hyper- and hypoglycemic states.

Appropriate use of test strategies requires not only an appreciation of analytic considerations and the ability of the tests to confirm or exclude the hypotheses, but also an understanding of the underlying pathophysiology and clinical features of the problems to be addressed. This discussion covers disease definition, pathophysiology, analytic considerations, and strategies for diagnosis and management.

Delayed pulmonary phosphatidylglycerol synthesis and reversal by prenatal dexamethasone in fetal rats of streptozotocin-diabetic mothers.

Lung slices from fetal rats of streptozotocin-diabetic mothers incorporated [3H]glycerol and [3H]choline into phosphatidylglycerol and disaturated phosphatidylcholine, respectively. When compared to age-matched fetuses from nondiabetic mothers, lung phosphatidylglycerol synthesis of 21-day fetuses of diabetic mothers was significantly diminished, although [3H]glycerol incorporation into other phospholipids was not impaired. Synthesis of disaturated phosphatidylcholine was not diminished in lungs of 20-, 21-, or 22-day fetuses of diabetic mothers. Prenatal dexamethasone partially reversed the diminished phosphatidylglycerol synthesis at 21 days of gestation; the degree of stimulation was the same as that seen in 21-day fetuses of normal mothers but the maximal rate of [3H]glycerol incorporation was about 60% of that in 21-day fetuses of normal mothers. Fetal lung disaturated phosphatidylcholine synthesis was not stimulated by dexamethasone in diabetic pregnancies, in contrast to that seen in nondiabetic pregnancies. These data suggest that maternal diabetes interferes with the ability of fetal lungs to synthesize phosphatidylglycerol, a finding consistent with the delayed appearance of phosphatidylglycerol in the amniotic fluid of human diabetic pregnancies. In addition, maternal diabetes impairs the responsiveness of disaturated phosphatidylcholine synthesis to dexamethasone. Since phosphatidylglycerol synthesis is enhanced by prenatal dexamethasone, this therapy may still be effective for reducing the adverse impact of maternal diabetes on fetal lung development.

Factitious hypophosphatemia related to mannitol therapy.

We observed factitious hypophosphatemia in a patient who was receiving large amounts of intravenous mannitol. Mannitol concentrations as low as 25 mmol/L inhibited phosphorus measurement by the Dupont aca endpoint method; a kinetic method was unaffected. The mechanism of the mannitol interference was binding to molybdate in the reaction, decreasing both the rate of color development and the endpoint measurement. We conclude that the molybdate concentration in the DuPont method is suboptimal for measuring phosphorus in specimens containing mannitol.