Cardioscreen NT-proBNP assay
When first presented with a potential 'cardiac' case it is often useful to have an additional screening process before embarking on more costly and time consuming examinations. Various cardiac biomarkers present in the bloodstream have been investigated for many years both in the human and animal field.
Natriuretic peptides are one of these biomarkers and are released from the ventricular myocardium during stress caused by cardiovascular disease. These particular 'cardiac neurohormones' comprise ANP, CNP and B-type natriuretic peptide BNP. BNP is synthesised as a prehormone (proBNP) and when released into the circulation is cleaved into the biologically active BNP and the inactive terminal fragment NT-proBNP. NT-proBNP has a long half-life compared to BNP and is therefore more easily detected in the bloodstream.
Once released into the circulation the physiological effects of the active BNP are many and include diuresis, peripheral vasodilation, inhibition of the renin-angiotensin-aldosterone system RAAS and the sympathetic nervous system.
Various studies have shown correlation between cardiac disease and the levels of NT-proBNP levels in the bloodstream. In humans in the emergency room setting a low NT-proBNP value has a good predictive value for the lack of cardiac disease as the cause for the presenting clinical signs of respiratory distress and shortness of breath. High values make cardiac disease 'very likely'. In a large number of human studies the level of BNP has been found to correlate to disease severity. Levels also give prognostic information.
An assay for NT-proBNP has now been developed for use in dogs where cardiac disease is suspected and is useful in the early stages of a clinical work up as part of the initial assessment before more costly and time consuming procedures, or referral may be required. NT-proBNP can also be used to distinguish between cardiac and non cardiac disease as the cause of dyspnoea and/or coughing in dogs.
This assay is useful in screening selective populations of dogs which are high risk breeds for cardiac disease, in particular cardiomyopathy where ventricular alterations occur:
- Cavalier King Charles Spaniel
- Doberman Pinscher
- German shepherd
- Bassett Hound
Other animals presented with common symptoms where heart disease is amongst the list of differentials can benefit from having levels of Nt-proBNP measured as part of the initial work up before further investigation of cardiac disease
- Shortness of breath
- Rapid breathing
- Easily fatigued
- Loss of appetite
- Reduced activity
- Aged animals over 6 years (depending on breed of dog)
- Those with existing heart murmurs
In dogs levels of NT-proBNP >300 pmol/l suggest heart disease is 95% likely. High 'normal' values must be interpreted alongside other clinical findings before proceeding further with any cardiac work up. Values below this would suggest seeking an alternative cause for the clinical signs, including respiratory disease, although it must be noted as with most tests available this is not 100% sensitive and occasional false negatives will be found.
Another important factor to remember is that sample preparation is crucial to obtain an accurate assay level and to avoid artefactual low (and therefore potentially negative) values to be obtained.
Sample preparation: Separated serum or EDTA plasma must be used for analysisSeparation should take place < 1 hour post samplingSerum/plasma should be frozenShip to laboratory for testing as soon as possible after sampling (sample need not be shipped frozen). Haemolysed samples cannot be tested.