amniocentesis test QF-PCR method

[Victorsmama]

Hello,

I am 33 and currently waiting for my second child. Got 2.8 mm at nuchal scan and it was said that the risk for carring a baby with Down syndroms has increased from 1/400 to 1/87. We decided to take amniocentetis test in order to be sure. I was told the quick QF-PCR method could give result within 2-3 days. We did get result from lab, but it said that the result is not informative and they have to now go for the traditional cell culture method so we have to wait longer. Does this mean that our risk is higher? Tried to find more information about how often QF-PCR method could fail but found nothing, what is the reason for that?

Thanks!
Anxious mama

[dollyp]

No idea I am afraid but bumping for you. I'm sure someone in the evening crowd will have more information for you.

[shhhh]

will bump as well as I hope someone comes along with an answer soon. Good luck xx

[ledodgyrobespierre]

NO it just means they could not get a definate result from the quick test this can happen if the specimen was contaminated with some of your blood cells this happened to me it just means you'll have to wait longer unfortunately but it does not mean the risk is greater.

[tamum]

bluebear will be the person to speak to about this, but IME PCR can fail for many, many reasons. Try not to worry

[mummymelling]

Hi there, im going for nuchal when im 11-13 weeks,how many weeks were you when you had yours done??,there are some very informative sites about measuring nuchal scans, and from what you say 2.8mm there isnt any thing to worry about as far as i can tell they worry if its 6++ and a 9+ gives an almost pos risk for downs .. hope this helps , its only stuff ive been trying to find out myself. hope all goes well for you xx

[Blandmum]

I had this done. The quick PCR can tast for some things, like downs and edwards, but cannot give the full screeing of the slower amnio result

and as Lrp posted the quick method can get contaminated

As Tamum says, try not to worry.

[Bluebear]

Hi, An uniformative result doesen't mean that your risk is any higher - it is normally caused by contamination of the sample by a tiny amount of DNA from you ( there is sometimes a little bit of mother's blood in the amniotic fluid sample) - because the QF-PCR technique is so sensitive it gets confused by having genetic material from baby and mum present.
The traditional cell culture method grows the fetal cells so should be able to give you a non ambiguous result.

[Highlander]

I'm surprised they went for PCR for a rapid result. FISH is just as quick, but less likely to give a false positive. In a nutshell, a fluorescent probe (different colour for each chromosome) is used to stick to the sampled DNA. It's very easy to see if you are carrying a baby with a trisomy.

Regardless of the result, all amnios are then followed up with a traditional manual karyotype.

[Bluebear]

HIghlander - PCR and FISH have been found to be equally as likely to give an inconclusive result. Some regions use FISH (normally small regional services as it is a cheap test to 'set up' but expensive for each patient. Others use the QF-PCR (Amplifying specific parts of the DNA of the baby using fluorescence to quantify the amount present) which is very expensive to set up but is much cheaper for each test if you are testing a large number.

[Bluebear]

Just wanted to add that FISH and QF-PCR have a 98-99% success rate (thought my post below made them sound rather unsuccessful).

[jabberwocky]

VM, I had an anmio back in July with this pg. We went for the FISH to get results quickly, but our dr./lab also automatically does the traditional culture as well. It wound up taking just over 2 weeks to get the results back from that one, so don't get too anxious if you don't hear anything in a week.