ACTH blood test for Cushings

[MochaDun]

I've had a Cushing's test done of an autumn previously (November) and about to have one soon again having seen the vet today for something else as I think we may be seeing sign or two of Cushings. Not sure if I have got this right but I thought from what I was told last time the ACTH hormone levels have a natural seasonal rise in the Spring as well as the Autumn. Is that correct about the Spring and does it matter therefore whether you test the blood in January rather than say Feb or March or is the month/s of Spring period of time irrelevant? I thnk I read somewhere not to test between July and October but I may have that wrong and just wanted to check for this time of year as want to get the best gauge of what's going on. Have been looking at the graphs on Talk about Laminitis PPID pages and Liphook one but only looks like they make adjustment to the refererence range for that late autumn seasonal rise for normal horses rather than any change in the Spring?

 

[UKa]

Hi, I am no expert but Talk about laminitis often offer vouchers for a free test exactly from July to October. I would test now if in doubt. If your horse has PPID it is likely yo show up all year round and you can start managing it. Good luck!

 

[_HP_]

http://www.thelaminitissite.org/ppid.html

This is a very useful, knowledgeable site and if you go to their Facebook page....EMS, PPID (Cushing's) and Laminitis UK , and ask, you'll get some good advice .

As far as I'm aware there is only one seasonal rise
http://www.thelaminitissite.org/s.html


http://www.thelaminitissite.org/ppid.html

*Can testing for PPID be done in the autumn during the "seasonal rise"?

Yes, definitely - in fact according to Liphook this may be the best time to test - "it is apparent that testing in the autumn may actually allow the greatest differentiation between PPID cases from normal horses and there is no reason at all to avoid testing for PPID in the autumn."
Obviously accurate interpretation of the results depends on applying properly derived and calculated seasonally adjusted reference ranges (which accompany all laboratory results from The Liphook Equine Hospital Laboratory), as ALL horses show an increase in ACTH during the autumn months (usually August to October).

However seasonally adjusted references ranges local to the horse should be used. Whilst Liphook have set their autumn cut off at 47 pg/ml (and 29 pg/ml the rest of the year), in Queensland, Australia 77.4 pg/ml is the autumn cut off being used (and 29.7 pg/ml the rest of the year) (however this has been verified against a gold standard of hirsutism plus 3 other clinical signs of PPID and therefore may only pick up advanced cases?).


Bear in mind the test can have false negatives, especially in early stages and should always be used alongside clinical signs

 

[vanrim]

Don't waste your money on the acth test as it is too unreliable and throws too many false negatives. I have 2 horses which between them have had approx 7 negative acth tests and just as many laminitic attacks. When they were tested using the thyroid response hormone test both were finally diagnosed as having Cushings and one horses's levels were through the roof! If you do some research on the internet you will find that current veterinary opinion is that the TRH test is really the one to use.