Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
(A) Percentages and absolute numbers of undetected trisomy cases among known trisomies. (B) False-positive T21 results among known euploid samples. The horizontal dashed line in each graph marks the 1% cut-off level often used in clinical screening.
