Gsn or Acgh?

[sobz70]

Hi there,
I wanted to ask about gsn and acgh, what is the difference and what causes less damage to the embryos?

[Carole]

Hi sobz70,

GSN is short hand for a type of chromosome testing of all 24 chromosomes (including X and Y) available through Gene Security Network- here's a link to their site http://www.genesecurity.net/preimpla...or-aneuploidy/ . aCGH stands for array comparative genomic hybridization (link to more info here http://en.wikipedia.org/wiki/Array_c..._hybridization) . aCGH is a newer method which resolves genetic differences down to much smaller pieces of DNA but for gender selection, either can resolve X and Y equally well. Neither should harm the embryo because the testing is done on some cells that are removed from the embryo for testing. Cell removal is the purpose of the the biopsy procedure. Unless the biopsy procedure is done poorly, the rest of the embryo should not suffer any ill effects from having a few cells removed, especially if biopsy occurs on day 5 when the whole embryo has 50-150 cells, compared to on day 3 when the embryo has only 8 cells. The cells that are removed for genetic testing are, of course, destroyed during testing. Hope this helps. Carole

[Carole]

I should also mention that GSN also offers array based methodology so in some cases people referring to GSN may be referring to array technology. Array is the next step technology for chromosome testing but older and newer methods are all capable of resolving X and Y chromosomes for gender selection.

[sobz70]

acgh does day 5 biopsy so we can have day 6 fresh transfer but gsn does day 3 biopsy so we can have day 5 fresh transfer am I right? I am worried about GSN- that embryos can self correct by day 5, what are the accuracies of these methods?

[nuthinbutpink]

To add on another thought- one reason I am not a fan of a lot of probes when there is no specific reason is the possibility of a false positive result. I know you did nit perform the analysis but what about biopsy timing- particularly day 3 biopsy of one cell. How do you know when the right time is to take the cell from the embryo? I mean, it us constantly changing, correct? How is the cell ever normal with the chromosome count? Is it possible the cell was dividing which yields an abnormal when it is in fact normal?

[jacqueline]

acgh does day 5 biopsy so we can have day 6 fresh transfer but gsn does day 3 biopsy so we can have day 5 fresh transfer am I right? I am worried about GSN- that embryos can self correct by day 5, what are the accuracies of these methods?

You can do 5 day biopsy with GSN too. If your IVF center is close enough to GSN (SF bay area) you can have day 6 transfer, otherwise they freeze.

[jacqueline]

aCGH is a newer method which resolves genetic differences down to much smaller pieces of DNA

Carole can you elaborate on this? Does this mean that aCGH gives more detailed results or is more accurate than GSN?

I am planning 3-day biopsy and still can't decide between aCGH or 5-probe. I am also concerned about false abnormals as NBP mentioned. I must decide today.

[Carole]

I have been asked the question about accuracy before and it's not something I dealt with as an embryologist. When I try to research it, numbers vary widely. The reason I am biased toward day 5 biopsy is that more cells are sampled and you are less likely to get a result that does not reflect the embryo. If you sample one cell on day 3, genetic mosaisicm (a variance in genotype among a group of cells that should be identical) could exist and by bad luck you sample a non-representative cell. Also troubling with day 3 biopsy is that you are removing a lot of biomass from the cell on day 3 (1/8 of the total biomass), sometimes this is too much for the embryo and it's progression is negatively affected. For detecting gender, you are looking for the absence or presence of entire chromosomes, not looking for single point mutations as you would for some genetic diseases so I think either should be accurate enough.

[Carole]

When we did day 3 biopsy, we would biopsy 8 cell embryos. Sometimes they were only 6 cells, sometimes they were more advanced (10-12 cells). 8 was the average number of cells. Our only criteria was to look for a nice round cell with a visible nucleus. The time lapse photography you see gives you a false impression. In all the times, I have checked on embryos, you don't see the actual division happening in front of you. They usually look static. If they look extra big relative to their neighbors, we wouldn't pick them because they may be on the verge of dividing. Timing of biopsy relative to cell division is not something you need to worry about. Carole

[CrystalTipps]

Hi Carole, I have some questions on GSN, if I may...

1. We have done two unsuccessful donor egg cycles. We did 5-probe both times. Our RE is recommending less probes next time, however I would be inclined to do more, given what's happened so far. If you were advising us, would you recommend more or less probes?

2. I have a child with a piece of Chromosome 16 missing. Is this something that would show up in GSN? We are using donor eggs so I am not worried about passing it on, but I am just very curious. Although having said that, I would not want another child with a bad chromosomal condition.

3. If you biopsy on Day 5, how many hours later do you need to do the Embryo Transfer? Would it be possible to leave it for 24 hours, or is that too long? i would not want to freeze as my clinic does not use the vitrification method.

Thanks,

CT.