Information on Accuracy of Maternal Serum Screening Test What are my chances of having a child with Down syndrome, trisomy 18 or an open neural tube defect if I receive a screen-positive result? Almost all screen-positive results are proven false when followed up with diagnostic testing because they only estimate the possibility that there is a birth defect. Conversely, normal serum screen results are seldom wrong and suggest that you need no further testing. Therefore, the best use of the test is to determine whether additional testing may be desired. Of all women who undergo the triple screen and receive a positive result,  a percentage will be false positives; that is, they suggest a problem when there really is none present. The actual percentage of false positives varies by the specific test protocol used; talk to your physician for the specifics for the test protocol used in your case. For more information, see: Should I have the maternal serum triple or quadruple screening test?