Cardiac Testing: Ruling Out, Not Screening In
Quick Answer — The cardiac biomarker earns its place in one specific moment: a dyspnoeic animal where the clinician must decide between cardiac and respiratory causes before imaging is available. In that setting, a low value meaningfully reduces the probability of heart failure. In an asymptomatic animal with a murmur, the same test produces mostly ambiguity and unnecessary referrals.
Quick Answer
Use it to exclude, not to discover.
The value of a negative
Diagnostic tests are usually discussed in terms of their positives. For NT-proBNP the more useful property is the negative:
| Result | Dyspnoeic cat or dog | Reading |
|---|---|---|
| Clearly low | Any | Heart failure unlikely; investigate respiratory causes |
| Intermediate | Any | Grey zone; imaging needed — do not treat on the number |
| Clearly high | Compatible signs | Heart failure plausible; but check renal function and age first |
A low value in a struggling animal is actionable within minutes: oxygen, cage rest, and a respiratory workup rather than diuretics. That is a decision the point-of-care platform can support before radiography or echocardiography is available.
The confounders that produce most discordance
| Confounder | Effect | Handling |
|---|---|---|
| Renal disease | Reduced clearance raises values | Interpret with creatinine/SDMA |
| Age | Values rise in some populations | Use age-appropriate interval |
| Pulmonary hypertension | Ventricular strain | Consider right-sided assessment |
| Sepsis / systemic inflammation | Can raise values | Interpret with the inflammatory picture |
| Severe respiratory distress | Physiology changes rapidly | Repeat after stabilisation where feasible |
The renal interaction explains most misleading results in cats, who frequently have both cardiac and renal disease.
Where the test does not help
- Asymptomatic screening. Low yield; false positives lead to echocardiography referrals.
- Distinguishing MMVD stages in a dog with a known murmur — imaging and clinical criteria do that.
- Screening cats for HCM. A normal value does not exclude early hypertrophy.
- Monitoring chronic therapy in stable patients, where clinical signs and imaging drive decisions.
Data pending. This section reports measured values from internal validation studies. They are published once the supporting study is complete; the current report is available from technical support on request.
Reference intervals and decision limits
Data pending. This section reports measured values from internal validation studies. They are published once the supporting study is complete; the current report is available from technical support on request.
| Population | Interval | Decision limit | Notes |
|---|---|---|---|
| Adult dogs | Pending pmol/L | Pending | Pending |
| Adult cats | Pending pmol/L | Pending | Pending |
Monitoring treatment
Where NT-proBNP is used serially — for example during hospitalisation for congestive heart failure — the trend can support the assessment of decongestion alongside respiratory rate, effort and weight. It should not replace those measures; it is an adjunct that can catch a patient whose clinical signs are equivocal.
Data pending. This section reports measured values from internal validation studies. They are published once the supporting study is complete; the current report is available from technical support on request.
Six traps
- Screening asymptomatic animals. False positives, unnecessary referrals.
- Ignoring renal function. The commonest cause of a misleading high value.
- Treating the number rather than the patient. Diuresis decisions need clinical assessment.
- Applying canine thresholds to cats. Different biology and limits.
- Excluding early HCM on a normal value. Imaging remains the reference.
- Comparing platforms mid-case. Trends across systems are uninterpretable.
The Author’s Take
Position. Cardiac biomarkers are the clearest case in this menu where the honest marketing claim is narrower than the obvious one — and narrower sells better to the clinicians who matter.
Reasoning. The obvious claim is “detect heart disease early”, which invites exactly the asymptomatic screening that produces false positives and eroded trust. The narrower claim — “resolve the dyspnoeic patient” — is bought by emergency and internal medicine clinicians who face that decision weekly, and it is the use case where a same-day result genuinely beats sending blood away. There is a second, less obvious benefit: a clinician who has used the test successfully to rule out heart failure once will trust it the next time a result is ambiguous. Trust in diagnostics is built from correct negatives far more than from impressive positives.
Disclosure. Written from published veterinary cardiac biomarker literature; no new experimental data. Values marked are placeholders for Migibio’s platform data.
Related pages
Sources
- Reference to be added.
- Reference to be added.
- CLSI EP28-A3c — reference interval methodology.
Frequently asked questions
- Is NT-proBNP a screening test for heart disease?
- No. In asymptomatic animals the yield is low and false positives generate unnecessary referrals. Its defensible use is ruling out heart failure in a dyspnoeic patient, and supporting triage decisions before imaging is available.
- What do renal disease and age do to NT-proBNP?
- Both can raise it. Reduced clearance in renal disease and age-related cardiac change can produce elevated values in animals without heart failure, which is why the result must be interpreted alongside renal parameters and clinical findings.
- Does a normal NT-proBNP exclude heart disease?
- It makes heart failure unlikely, but it does not exclude mild hypertrophy or early dysfunction, particularly in cats with early hypertrophic cardiomyopathy. Imaging remains the reference for structural disease.