[tri-med] Re: BLOOD TEST RESULTS

----- Original Message -----
From: "John Faulkner"
> OK, the blood test results come back for me. Also it really did not give
> any precise answers to my questions.

What exactly where your questions John?

>>Here is what it said:   chromosome
> bloodresult: 46, X Y, normal male karyotype.   Clinical information is
> required for the most accurate cytogenetic interpretation. If additional
> clinically relevant information is available, please call the Cytogenetics
> Department.

The referral did not specify to the lab doing the tests your clinical
symptoms for wanting a karyotype done. I gather this test was done to see if
you were the carrier of a genetic condition that may have caused Angella's
T-18. If so there would have been no clinical symptoms to report.

>>Why did they put in the second statement,  the following possibilities,
> although rare, cannot be ruled out?

Its a standard legal type disclaimer. They are covering their bases
essentially, in case something really rare is discovered later.

>>The following possibilities, although rare, cannot be ruled
> out: a) low level mosicism,

Mosaicism, is very variable, and can only be detected if the the sample that
they take contains trisomic cells. Sometimes the level of trisomic (or other
chromosomal anomaly) can be so small that it is not easily detected in
tests. How many cells did they karyotype? The more cells that they look at,
the greater the chance of picking up low level mosaicism. For example, if
they looked at 20 cells, just finding one cell would give you 5%, and if you
have less thatn 5% trisomy cells they may miss it. If they look at 100 cells
and find one thats 1%, but if the percentage of trisomy cells is less than
1% they may again miss it.

But also the very nature of mosaicism is that it can appear in some organ
systems and not in others. For example in Alex's case he has a high
percentage of trisomic cells by blood, but none detectable by skin. Its rare
but has happened in reverse where there is a zero trisomic count by blood
but skin is high.

b) very subtle rearrangements, and c)genetic
> disorders that cannot be detected by standard cytogenetic methods.

I cant be sure as you havent included the other information regarding the
test, but it sounds like they are covering the fact that they have only done
a g-banding karyotype. G-Banding will not show very tiny or subtle problems
with the chromosomes eg micro deletions. To do that they would need to do a
FISH or SKY test - and to do those they need a lot more information on what
they are looking for with regards to that subtle problem (that is they need
to make an educated guess as to what the problem is). FISH and SKY tests are
VERY specific.

I personally am not aware of any "subtle" problems that would cause T-18
though.............

Now
> can anyone tell me 100% for sure that I did not cause Angellaa's  Trisomy
> 18?

No one can ever guarantee 100% certainty with anything - but by having your
chromosomes checked you are improving your odds, and hopefully adding to
your peace of mind that this was indeed a one off event. We like to think of
genetics as being a very specific and exact science - unfortunately its not.

T-18 is in the vast majority of cases a sporadic occurrence - it is not
usually inherited. Inherited forms are usually easily picked up when they
actually see the child's karyotype. (the additional chromosome is usually
not in one piece and so they will look to the parents to see if they are
carriers of a balanced translocation)

I gather that Angella had a "straight" T-18, that is three complete 18th
chromosomes. So your chances of having a condition that would have "caused"
the T-18 were slim in the beginning. Checking your chromosomes adds more to
that slim by ruling out any obvious chromosome problem that would have
caused the T-18. So you went from very slim, to extremely slim.

He who never made a mistake never made a discovery.
-- Samuel Smiles

Keep Looking for Rainbows!!!
Karen, Mum to Alex (7, T-18 mosaic)
Sydney, Australia
http://members.optushome.com.au/karens
http://www.trisomyonline.org

                  Building ___ooOOoo__ Rainbows
                       www.trisomyonline.org
                  Families Helping Families On-line

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