The Effect of Lipemia on Insulin and Adiponectin Measurement in Equine Blood Samples

Lipemia is a common comorbidity in horses with obesity or equine metabolic syndrome, but the impact of lipemia on the measurement of insulin and adiponectin has not been evaluated.

To evaluate endogenous and exogenous lipemic interference with equine insulin and adiponectin measurements via several commercial assays.

Endogenous lipemia was evaluated using plasma and serum samples with triglyceride concentrations of < 40, 40-250, 250-500, 500-1000, and > 1000 mg/dL (n = 6 each). Sample insulin concentrations were determined via fluorescence enzyme immunoassay (FEIA), ELISA, and lateral flow assay (LFA). Test agreement was assessed using Pearson's correlation coefficient, Passing-Bablok regression, and Bland-Altman analysis. Exogenous lipemia was evaluated using pools of serum, plasma, and whole blood (n = 5 each) spiked with Intralipid 20% to triglyceride concentrations of 0, 50, 100, 250, 500, and 1000 mg/dL. Insulin concentrations were measured via FEIA, ELISA, and LFA, and adiponectin concentrations via immunoturbidometric assay (ITA). Interferograms were created and a Kruskal-Wallis test was used to compare bias between triglyceride concentrations.

With endogenous lipemia, agreement between the three assays was excellent (r > 0.90) with no appreciable impact of triglyceride concentration. For exogenous lipemia, significant (p < 0.05) negative interference was observed at triglyceride concentrations of 1000 mg/dL with the insulin ELISA using plasma. No significant interference was found for the insulin ELISA or FEIA using serum, insulin LFA using whole blood or plasma, or adiponectin ITA using serum.

Falsely low insulin values may be obtained at high triglyceride concentrations with the insulin ELISA using plasma.