Technical standards and guidelines: Prenatal screening for Down syndrome: This new section on “Prenatal Screening for Down Syndrome,” together with the new section on “Prenatal Screening for Open Neural Tube Defects,” replaces the previous Section H of the American College of Medical Genetics Standards and Guidelines for Clinical Genetics Laboratories

Abstract

21) is one of the most common genetic causes of moderate to severe mental retardation. Virtually all individuals with Down syndrome are hypotonic and have minor dysmorphic features, which can include up-slanting palpebral fissures, epicanthal folds, flat nasal bridge, Brushfield spots of the iris, shortened fifth finger, and transverse palmar crease. Congenital heart disease is present in 40%, and 5% have gastrointestinal anomalies such as duodenal atresia or Hirschsprung disease. The incidence of childhood leukemia is increased up to 20 times over that of the general population. Adults with Down syndrome experience neuronal degeneration identical to that present in Alzheimer's disease. Down syndrome individuals without congenital heart disease can live beyond 60 years of age.DS2.3 ETIOLOGY. Down syndrome is caused by the presence of an extra copy of chromosome 21, either as a free chromosome, a Robertsonian translocation, or a reciprocal translocation involving chromosome 21. Approximately 95% of cases result from sporadic nondisjunction during parental meiosis. The nondisjunction is maternal in 95% of cases, and 77% of the maternal nondisjunction occurs during meiosis I. The risk of having a child with Down syndrome increases with advancing maternal age. Down syndrome can be inherited when one parent carries a translocation involving chromosome 21. If a parent carries a Robertsonian translocation, the risk to the offspring is dependent on the sex of the carrier parent. DS2.4 LABORATORY DIRECTOR.Although the prenatal screening laboratory utilizes clinical chemistry methods such as enzyme immunoassays, its function differs, because the results require a unique kind of interpretation. This interpretation puts the results of the test into the appropriate context of a priori risks as determined by maternal age, gestational age, and family history. The laboratory director is often called upon to provide consultation regarding these risks and options for further action. To address these unique requirements, the laboratory director should meet the standards set out in Section B3 of the ACMG guidelines. When prenatal screening for Down syndrome is performed in a clinical chemistry laboratory in which the director does not meet these standards, the laboratory should have a demonstrated relationship with an individual Women and Infants Hospital, Providence, Rhode Island. From the G.E. Palomaki's present address is

The impact of temporal variability of biochemical markers PAPP-A and free β-hCG on the specificity of the first-trimester Down syndrome screening: a Croatian retrospective study

“…Most probably, some considerable analytical improvements may have occurred for free β-hCG and PAPP-A immunoassays on Immulite platforms since the year 2005, when Spencer published his study. Nonetheless, we can confirm that we have succeeded in keeping the high technical standards for biochemical marker analyses [24]. In line with Spencer's recommendations, the assessment of calculated risk variability is an obligatory and useful tool in quality control [25].…”

Triple Test Screening for Down Syndrome: An Egyptian-Tailored Study

“…The study was conducted on 668 Egyptian females making sure that at least a hundred participants were included in each week between 15 and 20 as has been recommended [17] . The American College of Medical Genetics and Genomics, (ACMG) technical standards and guideline for DS screening state that ideally 100 samples for each gestational week from 15 through 20 should be used to calculate medians [18] . Definition of gestational age was consistently based on measurement of fetal biparietal diameter to circumvent errors associated with last menstrual period calculations.…”