LAUSR

Abstract: Lipid accumulation disorders are common in psittacine birds and can be associated with changes in plasma lipoproteins, most notably low-density lipoprotein (LDL) and high-density lipoprotein (HDL). However, lipoprotein analysis by standard laboratory analyzers or an indirect method, such as the Friedewald formula, has not been validated in parrots. A research colony of 12 Quaker parrots (Myiopsitta monachus) were used to compare plasma values from the Roche Cobas c501 biochemistry analyzer for total cholesterol, total triglycerides, LDL, and HDL to gel-permeation high-performance liquid chromatography (GP-HPLC). To increase sample size and broaden the analytical range to include dyslipidemic samples, 2 cross-over studies were performed on a 0.3% cholesterol diet and a 20% fat diet. Agreement between methods was assessed by linear mixed models and Bland and Altman plots. The LDL concentrations calculated by the Friedewald formula and alternative formulas, and the effects of triglycerides on the biases, were also evaluated. Forty-five plasma samples were used. The cholesterol diet induced a marked increase in cholesterol and all lipoproteins, whereas the fat diet did not lead to dyslipidemia. Direct and indirect LDL measurements obtained with the clinical analyzer were not in clinical agreement with GP-HPLC, whereas HDL had acceptable agreement for normotriglyceridemic samples. Hypertriglyceridemic plasma samples were found to interfere with lipoprotein measurements. This study found LDL measured by the Roche Cobas c501 biochemistry analyzer and indirect estimations cannot be recommended in the Quaker parrot, and non-HDL cholesterol should be used instead. Lipoprotein panels obtained from hypertriglyceridemic samples should be interpreted with care.