[tri-med] Re: Amnio Issues

----- Original Message ----- 
From: <TRIER9
> I am fumbling through this discussion. Actually it is about false 
> positive's
> for Down syndrome. I know of 1 mom where this happened.....and then  of
> course I was asked HOW does this happen!

A false positive is really uncommon in an amnio - in a CVS its very 
possible, not so in an amnio if correct guidelines are followed.

Human error is the most likely problem - remember all karyotypes are done by 
human beans.

Not enough cells - possibly but only in the case of mosaicism.

Testing the mothers cells instead of the baby's - not usual in an amnio 
because only the first draw could contain contaminant from the mothers skin. 
The second draw should have had the mothers cells flushed out. Of course the 
operator could have been really bad and taken a sample of the placenta not 
the amnion but that should have been visually apparent from the draw.

Placenta has a chromosomal anomaly not the baby - thats very common and is 
called confined placental mosaicism. It is usually only detected in a CVS 
which takes a sample of the placenta NOT the baby or the amnion. An amnio 
should be clear of that.

So my best guess as to why it happens gets back to human error - samples 
mixed up along the way (hey it happened to Alex's original blood sample sent 
for karyotype) or simply an error in reading the reading the results. 
Chromosomal tests are 99.8% accurate - that 0.02% comes from 
somewhere...........

Life consists not in holding good cards but in playing those you hold well.
                                            -- Josh Billings

Keep Looking For Rainbows!!
   _--_|\
 /Karen \
 \ _.--._ /
          v Karen, Mum to Alex (11 years, T-18 Mosaic)
http://members.optushome.com.au/karens
 

                  Building ___ooOOoo__ Rainbows
                       www.trisomyonline.org
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