Can someone please explain to me what does it mean "false negative" and "falso positive" ?

[Anonymous]

I've read a lot these terms, regarding the NT + blood test done in the first trimester. What does it mean exactly?

Thanks,

[Anonymous]

False negative: test indicates there is no issue; in fact, there is an issue.
False positive: test indicates there is an issue; in fact, there is none.

[Anonymous]

"False positive" and "false negative" are misnomers when discussing screening tests; the NT and the quad screen assess whether there is a higher-than-normal or a lower-than-normal likelihood of chromosomal abnormalities. If the test indicates a higher-than-normal likelihood and there turns out to be no problem, that doesn't make the test wrong, any more than the weather report was wrong when it said there was a 60% chance of rain and it didn't rain.

It's worth noting that higher-than-normal on a quad screen still generally puts you in the very, very unlikely category: if normal for you age is one in a thousand and your factors put you at a .5% chance, that would be twice the risk, but still only one in 500.

[Anonymous]

I don't think I have ever heard of the triple screen being false negitive. But lots and lots of false positive, meaning person was told something was wrong, but nothing was.

[Anonymous]

Have you read "Choosing Naia," about a family whose daughter has Down Syndrome? The mothers triple screen showed that she was at exceptionally low risk for having a child with an extra chromosome. So it does happen.

Again, that doesn't mean a "false negative" which does not exist with screening tests. Screening tests are do not produce postive or negative results, they produce risk statistics.