The Bi-Test is a screening test performed in the first trimester of pregnancy. It is understood from the name that contains the word double or bi that it refers to 2 parameters that are measured. This test presupposes a simple blood test that the pregnant woman should perform on the day she performs the ultrasound for nuchal translucency. It is also called biochemical screening in Quarter I. The parameters measured by the Bi-Test are: free β-hCG and PAPP-A (pregnancy-associated plasma protein A). The combination of both of these parameters in the risk assessment for Down syndrome (or other chromosomal abnormalities) is more sensitive in screening than the use of only one of them. When maternal age is combined with the results of the Bi Test, the screening ability for Down syndrome reaches 60-65% with a false-positivity of 5%.
When is it performed? The Bi Test is performed between the 11th and 14th week of pregnancy.
What do you measure? Risk for chromosomal abnormalities: Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), Pattay syndrome (trisomy 13).
Advantages to Triple Test?
Higher sensitivity for the above anomalies.
Performed earlier.