Routine plasma biochemistry analytes in clinically healthy cats: within-day variations and effects of a standard meal

Limited information is available on pre-analytical variations in plasma analytes in cats. The objectives of this study were to assess the effects of the time of sampling and a standard meal on plasma analytes in healthy cats. Eight healthy, adult, fasted cats underwent blood sampling every 2 h from 8 am to 8 pm twice at a 12 day interval. On the days of sampling, four cats were kept fasted and the others were fed just after the first sample, in a crossover design. Plasma glucose, urea, creatinine, sodium, potassium, chloride, CO2, calcium, phosphate, proteins, albumin, cholesterol and triglycerides, alanine aminotransferase and alkaline phosphatase were assayed on each sample. Effects of time of sampling and meal on plasma biochemistry results were tested using a general linear model. Diurnal variations in tested plasma analytes in fasted cats were negligible except for urea and creatinine, which gave noticeably higher plasma concentrations in the afternoon than in the morning. Observed postprandial variations were of some importance for phosphate and creatinine and of indisputable clinical relevance for CO2 and urea.