acth stimulation test oddity

RE: acth stimulation test oddity

Annie Gleed — Sun, 08 Nov 2020 21:14:24 GMT

Thanks everyone for time and thoughts,

Ian : the dog currently does not look cushingoid (hair coat although present isn't as thick as a normal bichon) has no pot belly, dermal thinning and is not pu/pd as before. This particular case was a second opinion from another practice as is also on fortekor for an initially diagnosed renal issue ( high sdma and azotaemia, low sg and proteinuria). I have been wondering if both diagnoses are correct . But would assume that if this dog wasnt cushingoid it would have crashed by now since it is on 10mg vetoryl bid. I have seen some incorrect diagnoses (not all by me) and they have presented addisonian pretty quickly. Would love to hear your thoughts on this,

Annie

RE: acth stimulation test oddity

Ian Ramsey — Fri, 06 Nov 2020 17:18:28 GMT

Dear Annie,

I have seen this several times when we used to do a lot of ACTH stims for monitoring and we always checked it was not mixed up samples (by going over to our labs and looking at the original tubes again) and never found this was the cause. I know others in the filed have also seen this as well so you are by no means alone!

I am pretty sure that the explanation for your results is that trilostane simply can be more effective at blocking cortisol production than ACTH is at increasing it for at least a short time. These samples are measured on the same assay at the same time and the intra-assay variation of most assays is really low so the chance that this is due to inherent variation in the assay is less (if you measured the two samples a few days apart then it would be different).

Hope this helps

Ian

PS You said the dog was 'stable' on the current dose - I wondered if you meant no clinical signs or stable (but present) clinical signs?

RE: acth stimulation test oddity

Michael Woodhouse — Thu, 05 Nov 2020 23:43:12 GMT

[quote userid="12930" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/29473/acth-stimulation-test-oddity/226490#226490"]3) The lab could mix the samples up (I once had a cystocentesis cat urine sample which I packagaed and posted myself from a female, neutered, reported with sperm in it...)[/quote]

My mother is a biomedical scientist in a hospital lab. She just does biochemistry now, but her training involved all areas of the lab. Very common to find sperm in female urine samples........

[quote userid="24733" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/29473/acth-stimulation-test-oddity/226491#226491"]I do do pre-pill cort alone in some non stressed dogs but there is some schepticism about its reliability in stressy dogs. This is one of those cases so thought best to do acth stim. there is now a cheaper licensed tetracosactide so not as expensive as used to be.[/quote]

Irrespective, the level is too high so you need to increase the dose!

I do wonder if the Dechra monitoring advice will change now they have Cosacthen.

Some of these stressy dogs you can sneak a drop of blood for cortisol from them in the car park with a good nurse and then I think reliable. Much worse spending an hour in the practice barking their heads off (for the dog, the staff and the other patients)!

RE: acth stimulation test oddity

Annie Gleed — Thu, 05 Nov 2020 23:13:58 GMT

Thank you! So many possible answers!
grateful for your advice and time

Annie

RE: acth stimulation test oddity

Beats — Thu, 05 Nov 2020 23:13:55 GMT

[quote userid="24733" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/29473/acth-stimulation-test-oddity/226491#226491"]The lab assure me they also didnt make a mistake. [/quote]

And they probably didn't - the results just aren't that precise. But lab mix-up does happen - when I phoned to point out that they had found sperm in a female cat urine, they said perhaps it had been mated - once told it was neutered, they suggested perhaps it had an ovarian remnant - when advised that it had been in a cage in a veterinary clinic for a week, they advised that sperm can live a long time... one has to accept that sometimes a mistake with sample mix-up will occur and simply state that sample mix-up is highly unlikely as opposed to impossible!

RE: acth stimulation test oddity

Annie Gleed — Thu, 05 Nov 2020 23:05:59 GMT

I do do pre-pill cort alone in some non stressed dogs but there is some schepticism about its reliability in stressy dogs. This is one of those cases so thought best to do acth stim. there is now a cheaper licensed tetracosactide so not as expensive as used to be. The lab assure me they also didnt make a mistake.

RE: acth stimulation test oddity

Beats — Thu, 05 Nov 2020 23:05:34 GMT

HI Annie,

I've seen this a few times.

Possibilities:

1) The results just aren't that accurate - if you take 2 x samples in 2 x tubes from the same patient, I'm led to believe, you might get 2 x different results from your lab.

2) Siemens Immunolite (or whatever it is called) seems to have a problem with supplies or something - this is probably what your lab uses and could mean that point (1) is amplified further.

3) The lab could mix the samples up (I once had a cystocentesis cat urine sample which I packagaed and posted myself from a female, neutered, reported with sperm in it...)

4) The ACTH could have not worked due to bad batch etc (or gone intra-fat etc).

5) The vetoryl is working well and blunting the response to acth; and if you were to randomly sample the patient an hour apart without acth you would expect variation.

6) The patient already has very high ACTH levels due to removal of negative feedback from cortisol suppression, and giving more did nothing.

7) The patient was stressed prior to the first sample and was already producing maximum cortisol.

8) The timing of the test meant that the vetoryl was working more effectively at the second blood sample than the first.

EDIT - on a practical point for a busy first opinion practitioner, you are basing your interpretation of a post-pill ACTH stimulation test on a cushingoid dog on the POST-pill sample (I think) so I don't really think it matters what the pre-pill sample is (I used to sometimes just take and send the post-ACTH sample as lab fee for one cortisol was less than for two).

RE: acth stimulation test oddity

Michael Woodhouse — Thu, 05 Nov 2020 22:58:58 GMT

Why are you doing an ACTH stimulation on a diagnosed Cushingoid dog? I thought they decided cortisol pre- pill was more accurate and cheaper?

Was the dog stressed in the morning? Lab error?