Triple test

 ( Tests During Pregnancy ) 

The triple test, also called triple screen, the Kettering test or the Bart's test, is an investigation performed during pregnancy in the second trimester to classify a patient as either high-risk or low-risk for chromosomal abnormalities (and neural tube defects).

The term "multiple-marker screening test" is sometimes used instead. This term can encompass the "double test" and "quadruple test" (described below).

The Triple screen measures Blood serum levels of AFP, estriol, and beta-hCG, with a 70% sensitivity and 5% false-positive rate. It is complemented in some regions of the United States, as the Quad screen (adding inhibin A to the panel, resulting in an 81% sensitivity and 5% false-positive rate for detecting Down syndrome when taken at 15–18 weeks of gestational age) and other prenatal diagnosis techniques, although it remains widely used in Canada sogc.org and other countries. A positive screen indicates an increased risk of chromosomal abnormalities (and neural tube defects), and such patients are then referred for more sensitive and specific procedures to receive a definitive diagnosis, often prenatal diagnosis via amniocentesis, although the stronger screening option of cell-free fetal DNA screening (also popularly known as noninvasive prenatal screening) is frequently offered. The Triple test can be understood as an early predecessor to a long line of subsequent technological improvements. In some American states, such as Missouri, Medicaid reimburses only for the Triple test and not other potentially more accurate screening tests, whereas California offers Quad tests to all pregnant women. cdph.ca.gov

While the triple test can be performed at any point between 15 and 21.9 weeks of gestation, the highest detection rate for open neural defects is given by a test performed between 16 and 18 weeks of gestation.

1. alpha-fetoprotein (AFP)
2. human chorionic gonadotropin (hCG)
3. unconjugated estriol (UE₃)

An estimated risk is calculated and adjusted for the expectant mother's Ageing; if she is diabetic; if she is having twins or other multiples, and the gestational age of the fetus. Weight and ethnicity may also be used in adjustments.Henry's Clinical Diagnosis and Management by Laboratory Methods, 22nd ed. Chapter 25 Many of these factors affect the levels of the substances being measured and the interpretation of the results:

• As maternal weight increases, MSAFP level decreases
• African-American women have MSAFP levels that are 10-15% higher than those of Caucasian women for unknown reasons
• Women with insulin-dependent diabetes mellitus have MSAFP levels that are 20% lower than the rest of the population
• Having multiple gestations, such as twins, increases MSAFP because each fetus secretes its own AFP
• Incorrect estimation of gestational age is the most common cause of abnormal MSAFP levels

• Triple bolus test
• Cell free fetal DNA test

• AmericanPregnancy.org
• Risk and Down screening