NIPT - Fetal Fraction

mcrosie

I can't find a good answer on this online.

I got my NIPT results back and everything looks good. BUT there was only a 1% fetal DNA fraction, with a note that anything under 4% means:

"Test results from samples with a low fetal fraction may have reduced sensitivity for aneuploidy detection. A negative result from a sample with a
low fetal fraction is a valid result but there is an increased chance of a false-negative when compared to a negative result from a sample with a
higher fetal fraction."

Is this something I should worry about? The nurses at the doc's office didn't think it was a big deal - there was enough DNA there to give the results after all. I did have the test done at just 10w2d and I'm obese so that can lead to the lower fraction. 

tdevlindrye

I'm not that familiar with this situation, but I wouldn't be worried about it if I were you. Don't know if that helps. 

libbberty

@mcrosie, I just did a bunch of self research on this last night, and I think as long as the test isn't considered a "failure", the results are useful even if they're not 100% reliable. That said, your doc's office would probably ask for a redraw if they were concerned? I do think it's worth asking your doctor and not only the nurses about it just in case, but I also wouldn't worry. If you are concerned, I think you can also request a redraw with that 1% number, knowing you were so early in the pregnancy. But I tend to agree with your note that there was enough DNA to give results (and negative ones at that!), and that's a good thing. That said, I'm obviously not a genetic counselor, so I'd probably give my doc a call IF I were you (not saying you need to do that, just saying what I'd do because I am super conservative/anxious about that kind of thing).

One other thing I read that I personally found helpful - sometimes if one brand of NIPT doesn't give you enough fetal fraction, it's worth sending blood to a different lab. Most of them measure DNA differently so if your blood isn't giving one lab a lot of to work with, another lab might be better. I don't know how much truth there was in this comment, but I read it a lot yesterday - may also be worth asking about if you want more info.

BelhurstBride

I'd have a conversation with your doctor.

Do you have a history of chromosomal disorders in your family? If not, she might be fine with those results. But if you are in a higher risk pool she may want to re run the test or recommend the NT Scan. 

mcrosie

My doctor said nothing to worry about. I'm getting an NT scan next week at the high-risk clinic anyway, so that should catch anything else.

libbberty

So glad to hear that!