Plasma homocysteine concentration in privately owned healthy adult cats: assessment of biological determinants and establishment of a reference interval

The assessment of homocysteine status in diseased cats has indicated high plasma concentrations in chronic kidney disease and yielded conflicting results with respect to cardiovascular disorders. Previous investigations in small populations of normal cats revealed greater-than-expected variability in plasma homocysteine concentration. The purpose of this study was to determine biological determinants and the reference interval (RI) of plasma homocysteine concentration in the feline species, under strict pre-analytical conditions.

In this prospective observational study, privately owned healthy adult cats underwent a complete physical examination, urinalysis and blood testing, in order to rule out any signs of disease. Plasma homocysteine concentration was measured using high-performance liquid chromatography–tandem mass spectrometry.

Of 151 cats recruited, 30 cats were not included owing to abnormal physical examination or fractious behavior, and 30 cats were excluded based on abnormalities on blood work or urinalysis. Plasma homocysteine concentrations >28 µmol/l were associated with a dietary protein content >9.3 g/100 kcal metabolisable energy. The RI for plasma homocysteine concentration was determined to be 6.2–52.3 µmol/l.

Normal values for plasma homocysteine concentration in cats have a wide RI, suggesting high inter-individual variability. Whether some healthy cats exhibit impaired homocysteine metabolism remains to be elucidated.