Tri test: what it is and when to do it
The tri test, or triple test, is a set of biochemical tests carried out on pregnant women, used to trace a prenatal screening useful to provide an estimate of the probability that the fetus may be affected by chromosomal abnormalities, such as trisomy 21 (better known such as Down's Syndrome) or neural tube defects.
What is it about?
The tri test consists of a simple blood sample from the pregnant woman, before which fasting is not even necessary. This prenatal analysis is so called because there are three substances sought and analyzed in the maternal blood: alpha-fetoprotein (also called AFP), unconjugated estriol and chorionic gonadotropin. The latter are then evaluated together with other parameters (for example the patient's weight and whether or not she is a smoker) and compared with the reference values.
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When is it done?
Usually, the tri test is done between the 15th and 18th week of pregnancy, and since the values examined also vary according to the time of pregnancy, it is often accompanied by an "ultrasound scan.
Tri test: how much does it cost to do it?
The tri test, being a routine exam, is usually free and has an agreement with the mutual society, although there are often structures that require payment of a ticket. If, on the other hand, you go to a private facility, the cost usually ranges from 100 to 150 euros.
The values of the tri test
On the basis of the values examined by the tri test, disorders related to the fetus can be predicted and hypothesized. If, for example, the alphafetoprotein decreases between 25 and 30%, Down Syndrome can be hypothesized, if instead it increases it can be thought of defects of the neural tube or of the abdominal wall. In the latter case it is usually recommended to the patient to do an ultrasound to better understand. Even the unconjugated estriol, if it decreases, can suggest a case of trisomy 21 and the same when the chorionic gonadotropin has values of about twice the norm. If all the values suggest that there may be a high risk of Down Syndrome, we suggest amniocentesis, an examination that allows to exclude or confirm the result of the tri test. Unfortunately we know that amniocentesis presents a small percentage of abortion risk. (we speak of 0.5%), but it allows to directly analyze the chromosomal structure of the fetus. It is important to underline that the ability of the tri test to identify fetuses affected by neural tube defects is 90%.
Ultrasounds in pregnancy: what are they and when are they done?
Ultrasounds in pregnancy, as you have seen, are essential to follow the pregnancy and the development of the fetus. What exactly are they, and when are they made? In this video, Dr. De Mita explains everything there is to know!
Bi-test and quadruple test: what are they?
There are alternatives to the tri test. The first is the bi-test (or duo test) performed in conjunction with nuchal translucency (a non-invasive test), which is more reliable and is performed at an earlier stage of pregnancy. Then there is the quadruple test, which is the integrated tri test with dosage of inhibin A (a hormone that participates in the regulation of the menstrual cycle): the latter is used by those pregnant women who, for various reasons, have not been able to undergo the bi-test or the tri-test in good time.
