Do Cushings tests give false negatives?

[Snowfilly]

Not my pony, so I can’t get too involved… 15 yr old pony dropped top line, not shedding, had a run of minor infections this year - thrush, eye infection and been a bit scouring.

Been lame for a bit, suspected arthritis in then went catastrophically lame with laminitis on three legs almost overnight. Vet called. Tested negative for cushings, according to the blood test.

To me, she’s showing all the signs but I’m not the owner so I can’t push for a retest but is this a known thing with the tests?

 

[bluehorse]

Yes it is. Presumably the vet did the ACTH blood test? The owner should ask for a TRH stim test, its more reliable than the ACTH test. I know a horse that tested negative over a number of years with the ACTH test, owner eventually persuaded her vet to do the stim test and it came back positive. The pony had all the classic Cushings symptoms.

 

[Not_so_brave_anymore]

Definitely can. I would have thought the vet would be advising on what to do in this situation. I've got one on a prascend trial without even taking any blood because she's got such a needle phobia and vet couldn't get near her even with a double dose of IM sedative.

My gut feeling is that if the owners were hoping not to have to shell out for a lifetime of prascend, they will just take the negative test at face value and they won't want to hear any more about it. If they believe there's something else going on, they'll be in discussions with the vet already. (Fwiw it's a false economy not paying for the prascend- half a tablet a day for a whole year costs the same as two laminitis call outs ?‍)

 

[Pearlsacarolsinger]

Yes we had a horse that tested 'within normal range' on ACTH tests several times but we were suspicious of her symptoms and had the TRH-Stim test done, her level was 800 when 100 is the upper 'normal'

 

[meleeka]

it’s very common. I have a friend in the same position who refused to ask for the more accurate TRH stimulation test.

 

[throwawayaccount]

Yes it is. Presumably the vet did the ACTH blood test? The owner should ask for a TRH stim test, its more reliable than the ACTH test. I know a horse that tested negative over a number of years with the ACTH test, owner eventually persuaded her vet to do the stim test and it came back positive. The pony had all the classic Cushings symptoms.

the problem is knowing to ask for it, i wouldn't have known there were any other kinds of tests for cushing, apart from the standard :O unless thats just common knowledge and I wasn't aware, either way thank you for sharing that!

 

[Snowfilly]

Thank you all.

Owner is older and very much of the generation that ‘vets and doctors can do no wrong and must never be challenged.’ He’s just led by what they say and they’ve said the test was negative, so he’s gone along with it and is stabling, buting etc and assuming she’s negative.

Sadly his vet practice are ******* useless. They are at least coming back out to look at the mare again, I’ll see if I can persuade him to ask for the other test but he’s already talking of having her put down.

 

[vanrim]

In my opinion standard ACTH test is useless. I had loads of false negatives. Horse had uncontrolled laminitis for nearly 8 months. Was on so much bute she ended up in hospital with colitis. New vet recommended TRH test and her levels were through the roof. She is on Prascend and looking fab.