Please could somebody who has had experience with the tests give me some advice, I used these after my girl missed last season,
seeing such good results through these boards.
day 8 result - 2.1
day 12 result -2.5
day 17 result - 6.7
day 20 result - 17.8, lady called me from lab and said 24 -48 hours from the test, I took her to stud yesterday which was 24 hours from test and although my girl was keen, he was half hearted and no mating resulted, I would appreciate your thoughts.
thankyou

This should help you (taken from a previous CD thread):

0-2  nmol/L           Baseline concentrations too early to estimate ovulation
3 - 6 nmol /L        Minimum 2 days before ovulation expected however result of 3 - 4 nmol/L may persist for a week or longer before increasing. Earliiest estimating breeding 4 - 6 days but could be longer (re test needed)
7 - 12 nmol/L   Minimum 1 day before ovulation. Estimated window for breeding 3 - 5 days but could be longer  ( re test recommended)
13 - 18 nmol/L   Ovulation impending or just occurred. Estimated breeding window 2 - 4 days
19 - 31 nmol/L   Ovulation recently occurred. Estimated breeding window 1 - 3 days
32 - 64 nmol/L   Ova have matured, optimal potential for fertility.  Estimated breeding window  0 - 2 days
65 - 90 nmol/L   Ova have matured but aging, decreased potential for fertility.  Breed  at once
Above 90 nmol/L    Too late

I'll give you my experience, very recent and a first time IDEXer, always use Pre Mates in the past. Larry told me on my third test ( 20.2 Wed) she had ovulated on test day and that I could go Thurs but best wait until she is nearer 40 to 60 so wait until Friday so 48 hrs after ovulation. I did and got a mating Fri and Sat ( days 17 and 18) and she is carrying a large litter. If I were you Id just try again 48 hrs plus from her 17.8 result.

Diane

thankyou both, that is reassuring, because we are day 22 now it is quite nerve wracking thinking she may have gone over but I don't feel the levels would have gone up that quickly to have missed it yet.

I wouldn't worry, my girl was I think around 20 and Larry said take her in about 2 days, this was her third blood test and was mated on day 18.  I wish now that I had taken her back 2 days later, thinking maybe she would of had more pups and maybe she wouldn't of needed a c-section.  But hey she had one more than her previous two litters of two LOL! 

It does make you worry when the days are going into the 20's and thinking are you sure we haven't missed LOL!

seems like everybody has had good results going with blood tests, is it very unusual to be mating and getting a litter after day 22 upwards?

Think ill be using idexx next time had no luck with in house vet tests. If she was the norm you wouldnt be doing this and i had a litter from a mating day 26 dont give up its rising at least

>is it very unusual to be mating and getting a litter after day 22 upwards?

Not in my experience.  I had a girl mated on day 28 and had a litter.  Never say never.  :-)