I get my results this Monday. I have been told the number of repeats above 40 has no bearing on the onset or degree of severity or progression of the disease.
Doctors in Australia are reluctant to give patients the number of CAG repeats from their results.
Have I been given the correct information here or not. It seems to me that the number of repeats should have a bearing, but this is all very new to me.
If anyone out there has an answer I would be grateful.

You can't predict an individual's age of onset from the CAG repeats with the exception of when the scores is 60 or more - that usually indicates juvenile onset.

The CAG score does have a bearing on age on onset but only on average across a large population. If you take a thousand people or more with HD and plot out the average age of onset for each CAG number from 40 - 49, the average ages will fall on a straight line where the higher the CAG number, the earlier the age of onset.

If instead, you plot out each individual's CAG number and age of onset - so that each of those thousand people gets a point on the graph, you see a considerable amount of variation which is why prediction breaks down at the individual level.

Why the difference? Other genes probably modify onset (researchers have only found one that I know of at this point and it has a small effect), and there may be environmental factors such as trauma which could play a part, too - they just don't know yet. These factors will cancel themselves out in a large aggregate so that you can see the role of the CAG repeat number. But for any individual, there are too many unknown factors involved.

My mother and my sister both have a 41 CAG count and yet, my mother's onset was at 60 and my sister's was at 44.

Dear Marsha,
Thanks for clarifying this for me. It has taken me a while to get back to this.
As I said I was getting my results, well we as a family have been blown away.
My sister was getting her results the same day as me. We have discovered that not only does my mother have this disease, but my father now deceased from heart condition at 51, also carried the disease.
I got my dad's repeat of 35, my sister got my mum's 41 and my dad's 35.
My other sister has since received her reults and has the same 41 and 35.
We are in great shock and obviously very upset.
Through all of this though we are hopeful that help will be found soon, with the mapping of the human genome, we also have to hope or we would crawl into a hole.
I feel very fortunate to have the score i have, but at the same time I feel immense guilt that they are so much worse off than me. I'm trying to be a support to them but i feel sometimes that they don't want me around, like I'm too much for them.
Time I guess is a great healer and we all have a lot of grieving to do before we can move on.
Thanks again for the info.
Lesley