[Tri-test: clinical considerations on 1784 cases]

To evaluate the triple screen serum test as a noninvasive screening test for expectant mothers > 35 years old, who are not usually considered for invasive screening for trisomy 21.

1784 tri-tests (triple serum screening tests) were performed on expectant mothers between their 15th and 18th week of pregnancy, using the radioimmunological Ria-Kodak with an Alpha program (Logical Medical System LTD) with a cut-off value of 1:350.

244 positive equal to 13.60%. The percentage of false positives was respectively 12.9% (age < 35) and 28% (age > 35). Only in two of these cases did we have a positive response in amniocentesis for a fetus affected with Down syndrome. Of the 1540 patients with a negative tri-test, one woman gave birth to a fetus with Down syndrome.

Our study revealed a sensitivity of 66%. The elevated number of false positives has led us to decide on a variation on the cut off in the future: from 1:350 to 1:300.