Maternal Serum Screen 5 (Penta Screen) Test

The Penta Test or Maternal serum screen 5, Penta screen is evaluated to find the risk of a fetus having specific chromosomal abnormalities, like Down Syndrome (trisomy 21), Edwards Syndrome (trisomy 18) and Spina bifida or open Neural Tube Defects (NTDs). Maternal serum screening is a multiple marker test to estimate several substances in the blood of a pregnant lady during the second trimester (16-18 weeks) of pregnancy. NTD risk assessment follows the examination of AFP or alpha-fetoprotein alone, whereas, for Trisomy 18 (Down Syndrome) and Trisomy 21, multiple marker combinations are included ( AFP, hCG or human chorionic gonadotropin, unconjugated estriol or uE3, dimeric inhibin A or DIA, hyperglycosylated hCG).

Women in their second trimester pregnancy period are suitable for the Penta screen test. 14.0 to 22.9 weeks gestation period is also accepted for this test but the risk of NTD is not provided for samples before 15.0 weeks. Patient's age, weight, diabetic status, number of fetuses (women with more than two fetuses are not allowed), estimated date of delivery, are mandatory to know for the doctor. Other than these, no such preparation is needed.

• Prenatal screening is done to evaluate a pregnant woman's risk of carrying a fetus with chromosomal disorders, including Down Syndrome, Edward Syndromes, or Neural Tube Defects such as anencephaly or spina bifida. Positive screening tests are not solely diagnostic of a fetal anomaly. But it indicates the higher chances of having abnormalities.
• In case of Down Syndrome defects, the level of AFP decreases along with unconjugated estriol whereas, hCG and inhibin A levels remain high.
• Trisomy 21 defects can indicate a low level of hCG and uE3 while AFP level can be variable.
• Anencephaly or spina bifida disorders can show a higher level of AFP to pass into the mother's blood.
For more definite results, genetic counseling and cytogenetic studies of amniotic fluid cells are suggested. For this test, gestational age of the fetus must be accurately determined to avoid erroneous results.

• A blood sample is collected from an arm vein of the pregnant woman. Normal venipuncture process is used to collect a blood sample.
• Immunoassay is performed for detecting the levels of markers in the blood sample.
• Open Neural Tube Defect risk is dependent on the AFP marker along with age and insulin-dependent diabetes.
• Down Syndrome risk is based on all the markers and the maternal age at the delivery time.
• Edward's syndrome is based on Maternal age, AFP, hCG, uE3 markers.