nifty/harmony tests

[Elaine82]

Hi,
Has anyone who had a nifty or harmony test, had after a blood transfusion (within 6 months) before?
If you had a low risk result, was it correct when your baby was born?

[KittyandTeal]

I may be totally out here and you sound like you're more 'in the know' but I thought the harmony looked at baby's dna that was in the mothers blood stream, then scanned for chromosome and genetic defects.

Is the problem that there would be blood donors dna also present and therefore unable to tell if conditions picked up were baby's or donors?

Sorry I can't help but that's a really interesting question.

[Elaine82]

You are correct it does look at the babies dna in the mothers blood stream, I suppose the question is if there was a 3 persons dna, would this effect the test? Could it give a false negative result?

[SeanConnerysChestHair]

1. There are different types of blood transfusion, some only contain red blood cells which have very little donor DNA in them and most transfusions don't stay in the system for long so would not be there six months later.
   
2. Even if the blood transfusion was recent then as long as the blood donor did not have Down syndrome the Nifty or Harmony test would still work the same. There might be a small risk that, if the blood donor was male and the transfusion very recent, that the fetal sex might be misidentified as male but it would still be unlikely.

[KittyandTeal]

That's a good point, as T13 and T18 are incompatible with life (even those very rare survivors would not be able to concentrate to giving blood) those would not show.

I guess T21 is the 'wild card' but then there are usually earlier soft markers at the 12 week scan with blood test. So I guess if the donor had Down's syndrome then you could get a false positive.

Surely you wouldn't get a false negative as they'd screen 3 sets of dna for trisomies rather than 2?

[KittyandTeal]

Consent not concentrate obviously

[AnxiousKeziah]

I have not had a transfusion but did get a 1:2000+ result from Harmony. Later Amnio shocked us with a T21 diagnosis. Not common to get that, but I have learnt that a 1 in results still allows for the 1.

[KittyandTeal]

Anxious I'm so sorry to hear that.

We didn't have a harmony test but I was deemed low risk for all trisomies.

I was that 1:5000 that has a baby with T18. It's shit.