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N-Terminal Pro-B-Type Natriuretic Peptide (NT-proBNP) 1369

Causes of Abnormally High Levels • Endotoxemia and severe hypothermia can Specimen Collection and Handling
• Inflammation, whether acute or chronic, transiently shift neutrophils from circulating EDTA whole blood (lavender top tube) and
VetBooks.ir mation, left shift and/or toxic changes may • Destruction of mature neutrophils (e.g., to stain
infectious or noninfectious. If acute inflam-
freshly prepared blood smear for laboratory
to marginal pool.
immune-mediated neutropenia)
be present.
• Stress leukogram (glucocorticoids shift
neutrophils from marrow storage pool Next Diagnostic Steps to Consider Relative Cost: $$ (reported as part of CBC)
Pearls
and from marginal pool into circulating if Levels Are Low
pool) In absence of identifiable infection/inflammation, • Inflammation is not the only cause of
• Excitement leukocytosis (increased blood consider bone marrow aspirate or core biopsy neutrophilia; other common causes are stress
flow shifts neutrophils from marginal to leukogram and excitement leukocytosis.
circulating pool). Important Interspecies Differences • Extreme neutrophilia (>50,000 neutrophils/
• Paraneoplastic production of colony- • Neutrophilia from excitement is more likely mcL) is more often reported in dogs with
stimulating factor in young cats, whereas neutrophilia from localized inflammation at sites/lesions that
• Chronic granulocytic leukemia glucocorticoids (stress leukogram) is more start with a “p” (especially pyometra, but
• Canine leukocyte adhesion deficiency likely in dogs. also pancreatitis, prostatitis, pleuritis, peri-
(rare) • Dogs typically have greater degree of neu- tonitis). Other inflammatory diseases asso-
trophilia than cats. ciated with extreme neutrophilia include
Next Diagnostic Steps to Consider • Cats may have benign idiopathic neutropenia hepatozoonosis and immune-mediated
if Levels Are High (diagnosis of exclusion). hemolytic anemias.
Assess for cause depending on clinical signs. • Mature neutrophilia can be a useful descrip-
Drug Effects tive term, as it indicates that no bands or
Causes of Abnormally Low Levels • Increase: glucocorticoids left shift is present.
• Intense inflammation, especially if bacterial • Decrease: albendazole, methimazole, AUTHOR: Stephen D. Gaunt, DVM, PhD, DACVP
cause (increased tissue demand) trimethoprim-sulfa, phenobarbital, many EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
• Decreased granulopoiesis (e.g., feline leuke- chemotherapeutic anticancer agents
mia virus [FeLV] or feline immunodeficiency
virus [FIV] infection, drugs [see below],
myelophthisis)
• Acute parvoviral infection (decreased marrow
production and endotoxemia)

Laboratory Tests
N-Terminal Pro-B-Type Natriuretic Peptide (NT-proBNP)

Definition Cat: Lab Artifacts
Circulating biomarker for cardiac disease in • < 100 pmol/L within reference interval Prolonged contact with glass, delayed separation
dogs and cats • 100-270 pmol/L slight increase; cardiac of cells from plasma, and improper or prolonged
workup suggested if clinical signs present storage will decrease values.
Synonym • > 270 pmol/L consistent with heart disease
BNP Specimen Collection and Handling
Causes of Abnormally High Levels Plasma (preferred in dogs) or serum. Contact
Physiology Increased intracardiac hydrostatic pressure. laboratory for specific specimen requirements.
Natriuretic peptides of both A- and B-type Lung disease, presumably by causing cor Special protease-inhibitor (pink top) tubes
(ANP, BNP) are produced by myocardial tissue pulmonale (minimal increases). Azotemia (renal, required previously, now generally unneces-
and released into circulation in response to prerenal) and dehydration may cause slight sary. For in-clinic tests, follow manufacturer’s
increased pressure and wall stress. BNP occurs increases. instructions.
in circulation in two forms: biologically active
but unstable C-terminal BNP and biologically Important Interspecies Differences Relative Cost: $$
inactive NT-proBNP. The NT-proBNP form has The assay is a species-specific ELISA test; the
a longer half-life, and increased serum concen- canine assay cannot be used on feline blood Pearls
tration has been correlated with cardiac disease or vice versa, nor can the human assay be used • Patients with pulmonary hypertension or
in dogs and cats. Daily variation is reported. on blood from either species. renal disease may have elevated NT-proBNP
concentrations.
Reference Interval Drug Effects • Serum NT-proBNP levels help differentiate
Dog: Drugs used for treating cardiac disease (diuret- between dyspneic patients with cardiogenic
• < 900 pmol/L within reference interval ics, angiotensin-converting enzyme inhibitors, pulmonary edema (high NT-proBNP)
• 900-1800 pmol/L slight increase; cardiac beta-adrenergic receptor blockers, vasodila- and dyspneic patients with noncardiac
workup suggested if clinical signs present tors, antiarrhythmics) may decrease values disease (normal NT-proBNP) in both dogs
• > 1800 pmol/L consistent with heart disease slightly. and cats.

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