PPID - false negative results with ACTH test

Suby2

Suby2

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Does anyone have any experience of their pony/horse having false negative results from the ACTH test? I had problems for several years with my (20 year old pony) and numerous vet visits. Although she was tested for PPID her results were only ever marginal for it.

As she still wasn't 'right' I had her tested for stomach ulcers at the vet's premises and while she was there and they had a chance to study her they realised how her appearance was typical of a Cushing's pony and she was put on Prascend straight away. She also had the other test (can't remember the name) which confirmed her condition. The vet now says to just treat her by her symptoms rather than the ACTH test.

Although she improved well enough for me to be able to hack her out gently she has now gone very flat again - she got very lethargic previously. I contacted the vet as I thought it might be due to the autumn rise and perhaps she needed her Prascned increasing temporarily, however the vet thought that it was late in the year now and just to see how she goes. Other than the lethargy she is well in all other respects and her diet and management are closely managed.

I should mention that she also has EMS, SPRAO and arthritis but all are under control.

It's just so frustrating seeing her down after she got back to looking her old happy self :-(
 
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yes I have. Mine was tested twice and the second time only managed 11 (<29) yet he had every cushings symptom possible. I trialled prascend and work purely on symptoms. I increased prascend mid September to 1.5 and it improved things. The vet is often not much help in these cases as you are the one who sees the horse every day and knows it so well. It is a case, if you are monitoring by symptoms not tests, of studying everything and trying to work out when more is needed. It is not an exact science. i considered retesting but then decided I wouldn't believe the results. If they were low would it just show again a false negative or would it mean the cushings was under control.
If you had her under control and she was doing well and vet says to treat her by her symptoms why not just increase by half a tablet for a month and see what happens? Keep records and if she improves you have your answer if she doesn't then perhaps there is something else. To me this is still a little early to reduce (or not increase) a dose.
 
Thank you both for your replies, having heard of your experiences I will up her dose by half a tablet (she is currently on one per day) and see if she improves.

paddy 555 - how long did it take for you to notice an improvement on the increased dosage?

One thing that I see as a problem is that I get my Prascend using a vet prescription which obviously only allows for one tablet per day, so although I have plenty at the moment, in theory I would have to ask the vet for extra tablets. But, if I do that I am basically saying that I don't trust the vet's opinion and am going to ignore it!
 
Suby2 said:
Thank you both for your replies, having heard of your experiences I will up her dose by half a tablet (she is currently on one per day) and see if she improves.

paddy 555 - how long did it take for you to notice an improvement on the increased dosage?

One thing that I see as a problem is that I get my Prascend using a vet prescription which obviously only allows for one tablet per day, so although I have plenty at the moment, in theory I would have to ask the vet for extra tablets. But, if I do that I am basically saying that I don't trust the vet's opinion and am going to ignore it!
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4 weeks but that is the time for mine. Different times for different horses. Some react very quickly, some take longer. i think around 2 months would be considered reasonable.

No you don't have to imply you don't trust the vet. I am sure they realise in this situation that you have to take some initiative and try and work out what is best. If your vet said to treat her by symptoms that is exactly what you will be doing. When you have to go back for more tablets just explain you had to increase by a half due to x, y and z symptoms. Explain it improved the horse and it stabilised or explain that having tried it you found it didn't make any difference. I just explain to mine what I have done and why.
 
Mind had a false neg with the ACTH test, diagnosis was confirmed by the TRH test.

My vet would not prescribe Prascend without a positive test result, despite the symptoms being fairly obvious. He wanted to be sure of the dose. I found this frustrating but could understand his reasons.
 
The first one I had done on my horse, September 2014, in the seasonal rise, came back at 18. I KNEW it couldn't be right but when the seasonal rise ended in October I sort of forgot about the symptoms and recurring LGL. When they presented again early this summer I started him on Prascend and built to 1mg/day. A test this August, on 1mg/day, returned a level of 28.
It was a different vet, the first one was done by a vet who did free visits so he would organise a cluster of calls before returning home some 25 miles away. I suspect he didn't get the sample home in time - it can be critical that it is treated as per the protocols. I know someone else who had several false negatives and finally confirmed diagnosis by a Prascend trial, for me that is a much more reliable way.
 
The more I read about the results and symptoms the more I think there are horses out there being treated unnecessarily and vice versa. I had one of my horses tested 'just in case' as the vet was there and the test was free. He had a reading in the low 70's despite not having any symptoms. I am monitoring him.
 
It's pretty common to get a false negative, especially at the 'beginning' of the condition. I'm amazed vets don't routinely warn that it could be a false negative!
 
FFAQ said:
It's pretty common to get a false negative, especially at the 'beginning' of the condition. I'm amazed vets don't routinely warn that it could be a false negative!
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Seems so, although the equine vet who did mine and with whom I discussed a Prascend trail, said it was extremely unlikely!
 
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