[tri-med] Re: question regarding genetic tests: Cells counted etc

----- Original Message ----- 
From: "Barbara Farlow"
> I don't think the FISH really tells me much. It says the probe signals are 
> compatible
> with trisomy 13 in a female.

Ooooo they are cheeky. They didnt do a count. Not good and very sloppy in 
this day and age. Are you sure that there is not a line with a whole lot of 
numbers and possibly letters? It could read like this

(LSI CEP 18) x 2 {425} (LSI CEP 18 x 3 {184}

OK let me type out Alex's first FISH report. You have to read the whole 
thing. This one was done in 1997

FISH analysis with the 18 alpha-satellite probe (D18Z1, Oncor) showed no 
evidence of Trisomy 18 in the tissue in 200 cells scored. This suggests that 
a trisomy 18 population is not present. Probes used have not been approved 
by the FDA and the above data are not to be construed as the results from a 
stand alone diagnostic test. These results are provided for informational 
purposes only and should be interpreted only in the context of established 
procedures and / or diagnostic criteria.

So no count was done because there were no additional signals to count.

And this is another done in 2006

Chromosome identification by FISH
Probes employed - prefix indicates type of probe
(L - locus specific; C - centromeric; T - telomeric; W - whole chromosome)
Probe(s)     CEP X/CEP 18
No. cells nuclei examined    609
Karyotype    mosaic trisomy 18 (see below)

Results / Interpretation

nuc ish (LSI CEP 18) x 2 {425} (LSI CEP 18 x 3 {184}

FISH analysis on skin using a chromosome 18 specific probe showed that 30% 
(184 / 609) of the cells contained three chromosome 18 signals
Rgis is consistent with a mosaic 18 karyotype

FISH signals consistent with the presence of one X and one Y chromosome were 
also observed.

Thats the end of the relevent info - along with that FISH there is a 
G-Banding report and that gave the 33%. Similar results but if push came to 
shove the G-Banding is the result used even though its a smaller number of 
cells.

> The abnormal result is based on scoring of a minimum of 50 interphase 
> nuclei and 70% or more
> and 70% or more of the nuclei having the same abnormal number of signals.
> Mosaicism and abnormalities of chromosome structure are not detected by 
> this method.

No because they are doing it grossly (as opposed to closely) and rapidly and 
allowing for artefact, mind you from what I understand thats a large 
artefact margin. Artefact margin goes with the less than 5% stuff not 
reported that I talked about in the other email.

If they didnt do the count its slack but valid because each lab sets their 
own standards. I presume that they are accredited, though after checking 
into what accreditation for a lab means it doesn't hold much credit with me 
because they dont have to report errors or things like that - so long as 
they look good on the day and the books are up to date thats accreditation.

> I am unclear how this info can help.

You need that line with the numbers but it could be written a million ways. 
Can you scan or fax me a copy of the original document along with the 
g-banding report. There is no standardised way of writing this information 
and it could be there but "hidden". Its just hard (for me) to see the entire 
picture without seeing it in front of you sometimes.

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 (14 years, T-18 Mosaic)
http://members.optushome.com.au/karens

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

Other related posts: