Prenatal Screening – Maternal Serum Screening/Quad Screen
|Test description||Prenatal maternal serum screening consists of measuring four chemical markers present in the mother's blood during pregnancy: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (uE3), and dimeric inhibin A (DIA). Abnormal levels of these chemicals may indicate increased risk for neural tube defects (NTDs), Down syndrome, or trisomy 18. This screening test detects approximately 85% of neural tube defects, 70% of Down syndrome, and 60% of pregnancies with trisomy 18. Approximately 5% of all pregnancies tested will have an abnormal screening test requiring additional diagnostic testing. However, most of the pregnancies with an abnormal screen will result in a healthy baby, and only a small number will be diagnosed with an NTD, Down syndrome, or trisomy 18. Inaccurate pregnancy dating (gestational age) and the presence of twins or other multiples can cause an abnormal screening result. Pregnancy dating by ultrasound will ensure the most accurate test result. Maternal age, race, maternal weight, twins, and maternal diabetes are also important factors in the interpretation of the results. Genetic counseling and prenatal diagnostic testing should be considered with any positive maternal serum screening result.|
|Indications||The maternal serum screen is a blood test available to all pregnant women to identify pregnancies at increased risk for neural tube defects, Down syndrome, and trisomy 18.|
|Specimen Requirements||3-5 ml of blood in a red top tube or 2 ml serum (no anticoagulant) between 15 and 20 weeks gestation.|
|Transport||Transport samples at room temperature by first class mail or overnight courier on the day the sample is obtained. Protect from extreme temperatures when necessary. If shipment is delayed, serum sample may be stored up to 6 days at 2-8 degrees C. For longer periods, store samples at -20 degrees C. Repeated freezing and thawing should be avoided. Do not freeze whole blood.|
|Turnaround time||7 days|
|CPT Codes||82105, 84702, 82677, 86336|
The Biochemical Lab provides diagnostic and screening tests for a variety of inherited metabolic disorders.