Chorionic villus sampling

Citrullinemia. Neonates with AS deficiency usually die, and most survivors suffer major brain injury. Patients with a partial deficiency may have a milder course, and a few individuals with citrullinemia have been phenotypi-cally normal. The diagnosis usually is apparent from the hyperammonemia and the extreme hypercitrullinemia. The activity of AS can be determined in both fibroblasts and chorionic villus samples, thus simplifying the problem of antenatal diagnosis. 

The increased risk of trisomy with advanced maternal age motivates more than half of pregnant women in North America to undergo prenatal diagnosis (most commonly, amniocentesis or chorionic villus sampling, discussed in Oiapter 6). Down syndrome can also be screened by assaying maternal serum levels of a-fetoprotein, chorionic gonadotropin, and unconjugated estriol. This so-called triple screen can detect approximately 70% of fetuses with Down syndrome. 

The specimen will be the basis for the analytic analysis. Is it RNA or DNA What is the origin of the tissue Amniocentesis Was it a spontaneous product of conception Were anatomic pathology slides or tissue blocks prepared Are cell lines involved Are these primary or immortalized Was a chorionic villus sampling procedure done Is the sample properly collected peripheral blood The answers to each of these questions should be noted, and considered part of the validation of a useful nucleic acid extraction method. A molecular diagnostics laboratory should adhere to the highest standards in providing services, and prior validation of applicable nucleic acid extraction procedures is a must to ensure high-quality service. 

Prenatal analysis Chorionic villus sampling or cultured amniotic fluid cells... 

Antenatal diagnosis is possible by chorionic villus sampling. 

Jansen MW, Brandenburg H, Wildschut HI, Martens AC, Hagenaars AM, Wladimiroff JW, Veld PA, The effect of chorionic villus sampling on the number of fetal cells isolated from maternal blood and on maternal serum alpha-fetoprotein levels, Prenat. Diagn., 17 953-959, 1997. 

Male fetuses with 50 to 230 copies of the repeat should be asymptomatic, whereas those with more than 230 copies will have fragile X syndrome. Female fetuses with 50 to 230 copies also will be asymptomatic however, it is difficult to predict the extent of mental retardation in female fetuses with more than 230 copies of the repeat. Although hypermethylation of the CpG island is a poor prognostic indicator, it is not always present in DNA extracted from chorionic villus samples (Sutherland et al., 1991). Empiric data showing that female carriers with full mutations have nearly a 50% risk of mental impairment should be considered reliable. 

Investigate potentially fife-threatening disorders of Hb synthesis in the fetus and is performed at less than 10 weeks gestation on chorionic villus samples... 

Prenatal diagnosis can include fetal ultrasound, maternal serum studies, or sampling of cells from the fetoplacental unit by chorionic villus sampling [CVS at 8 to 10 weeks, amniocentesis at 12 to 18 weeks, or percutaneous umbilical sampling (PUBS) from 16 weeks to term]. 

Likely test Oligonucleotide probe. After chorionic villus sampling is performed, a radioactive probe can be used and hybridized with specific genetic mutations in the fetus deoxyribonucleic acid (DNA), allowing for prompt detection and prenatal diagnosis. 

Chorionic villus sampling Colposcopy Cytomegalovirus Endometrial biopsy Estriol excretion Fetal biophysical profile Fetal contraction stress test Fetal nonstress test Fetal scalp blood pH Fetoscopy... 

UUman S., Nelson L.B., Jackson L.G., Prenatal diagnostic techniques. Chorionic villus sampling. Survey of ophthalmology 30 (1985) 33-40. 

Johnson JL, Rajagopaian KV, Lanman JT et al. (1991) Prenatal diagnosis of molybdenum cofactor deficiency by assay of sulphite oxidase activity in chorionic villus samples. J Inher Metab Dis 14 932-937. 

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