False positives proBNP & troponin?

Re: False positives proBNP & troponin?

emma_j — Wed, 10 Sep 2014 15:38:03 GMT

Thanks Graham

I'm not in work this afternoon so don' t have the case notes to hand, so I'll get in touch tomorrow.

Re: False positives proBNP & troponin?

Graham Bilbrough — Wed, 10 Sep 2014 07:32:28 GMT

Good morning

Yes, I am around.

I think others have covered my first thoughts: renal failure, hypertension and hyperthyroidism. Shall we chat on the 'phone? Send me a PM with your practice details and I will give you a call. I will then update the forum.

Best wishes

Graham

Re: False positives proBNP & troponin?

emma_j — Tue, 09 Sep 2014 22:00:00 GMT

Frustratingly, no T4 was included on the initial bloodwork and it's now too long past submission to request it be run on the previous sample. Symptomatically the cat isn't screaming hyperthyroid but of course it's quite possible. It's a very good point that the scan is carried out by an ultrasonographer not a cardiologist and that is a point that has been raised with previous cases!

Cat is asymptomatic and o is not keen for anything further at present, we discussed various options, and have agreed to monitor in 3 months - noted in the plan to include T4, BNP, full biochem/haem/urinalysis, and if BNP raising then consider rpt scan, poss referring for a cardiologist 2nd opinion rather than our usual visiting ultrasonographer.

I'll try and remember to look up the case in a few months and see what transpires! In the meantime Graham if you are around would still be interesting to hear your take on this.

Re: False positives proBNP & troponin?

Kate Richardson — Tue, 09 Sep 2014 18:03:14 GMT

I assume remaining bloods were normal (and I am assuming and routine biochem/cbc/urinalysis and T4 were performed)? Any other symptoms such as weight loss? I agree with Martin, check BP, but surely hypertension should cause changes detectable on echo if enough to raise BNP. The other question, without meaning to question your ultrasonographer, is how confident/experienced are they with echo- we also have a very experienced visiting imager who is a European specialist, and whilst she is happy to perform echos, she has always made perfectly clear that she is not a cardiologist. Did your imager do a full echo including Doppler/colour flow/velocities etc. Otherwise if the cat is normal it may be that this is a normal result for this cat, or is it possible there was transient cardiac pathology? Just thinking outside the box!

Re: False positives proBNP & troponin?

Martin Atkinson — Tue, 09 Sep 2014 18:00:09 GMT

I was going to say that a 15 year old cat with a grade 3/6 murmur would be of less concern to me than an 8 year old cat. That said my 15 year old was diagnosed with hyperthyroidism, stage 2 CKD, mildly hypokalaemic, moderate hypotension and had an NT-proBNP of >1500. I did a thyroidectomy, put him on amlodypine, benazepril, Kaminox and low dose aspirin. He's now euthyroid and normotensive and he's staying on the meds!

Re: False positives proBNP & troponin?

An On MRCVS — Tue, 09 Sep 2014 17:57:08 GMT

Re: False positives proBNP & troponin?

emma_j — Tue, 09 Sep 2014 17:46:25 GMT

It wasn't me that requested the troponin so can't help you with the reasoning there I'm afraid! My current role is as a floating vet for a large group so I rarely have my own cases from start to finish.

It's booked in for later this evening, plan is to auscultate the cat myself to see if I agree with the murmur grading, have a chat with o about any symptoms at home, and gauge how they feel about ongoing monitoring etc, thinking along the same lines as you.

Wrt renal function/hypertension - I can't see that a BP was done, creatinine of 146 with a urine sg 0f 1.041, so no significant renal concerns at present.

Re: False positives proBNP & troponin?

Martin Atkinson — Tue, 09 Sep 2014 15:56:13 GMT

The factors that can cause a raised (rather than artefactual) NT-proBNP relate to hypertension most especially due to renal disease so it would be useful to know the blood pressure and renal function. However IME and from research I've read there has to be marked renal disease and hypertension to effect this and then only tens rather than hundreds of pmol/l.

The figure of 270 is very much a guide and although some cats may have significant cardiac disease above this again IME in a series of 40 cats none showed signs of cardiac failure with a BNP below 350. However, I did have one cat which I believed had symptoms of cardiac failure and a BNP of >350 (can't remember the exact figure now) and the cardiologist at a referral centre said it's scan was normal. I asked them to re-visit it and a more experienced clinician decided that actually there was some left ventricular wall thickening.

Personally I would talk through this with the client and explain the discrepancies on the tests, especially as it has apparently gone from no murmur to 3/6 in less than a year, and at the very least repeat the BNP in a few months time or ask whether they would rather treat this cat unnecessarily for a while or risk it dropping dead! We're always wiser in hindsight.

I don't have any recent experience with Troponin in cats so it would be interesting to hear your reasons for performing it as the last time I heard there was a cat specific test in the pipeline. Troponin historically was only of use in damage to the myocardium such as in infarcts but I read that although we don't recognise this disease in cats, PM examination have revealed multiple infarcts in cat hearts. Maybe Graham Bilborough will be along soon as I believed this was his baby.

Re: False positives proBNP & troponin?

emma_j — Tue, 09 Sep 2014 15:35:07 GMT

No murmur was not noted - goodness me, post-prandial brain fog here. No murmur was noted at the time of the dental work earlier in the year!