Reference Laboratory




Prenatal Screening Tests

Our laboratory uses test analysers with the immunochemiluminescence technique and the PRISCA program. These tests allow us to determine Trisomy 21 (Down Syndrome) open neural tube defficiency (NTD) Trisomy 18 and Trisomy 13 risks during pregnancy; they do not however provide for a definite diagnosis. Or laboratory is able to undertake dual, triple, quadruple, combined and integrated tests as well as the AFP test. These are non-invasive tests relying on ultrasound readings and samples of blood taken from the mother to determine the levels of certain hormones in the blood at specific periods of the mothers’ term of pregnancy; they pose no risk in child loss. During weeks 11-14 in the dual test PAPP-A and free β-hCG; while in the combined test and in addition to the PAPP-A and free β-hCG some ultrasound readings of the unborn infant are taken. In the triple test during weeks 14-22 AFP, total hCG and uE3 is tested for; and for the quadruple test following that in addition to the triple test inhibine –A values are identified.

The integrated test is made consecutively; the first, during weeks 11-14 a PAPP-A measurement of the mothers blood sample and a neck sizemeasurement (NT) of the infant. The second of these is done during weeks 16-20 and checks for AFP, total hCG and uE3 with the addition of inhibin Ameaurements to obtain a risk value.

The AFP test, determines the risk of NTD (neural tube defect) by means of a blood sample and is obtained by comparing the AFP value to pregnacy term in weeks.In addition to the hormone values obtained through a sample of the mothers blood, as above, a form is prepared which outlines information regarding the expecting mother race and whether she smokes, has diabetes, her number of pregnancies, if the pregnancy is through IVF methods, if previous pregnancies had a chromosome or NTD history. The probability of risk is then calculated by a statistical program which uses this information and the results obtained.