Comparison of assessment techniques: plasma lipid and lipoproteins related to the metabolic syndrome

BACKGROUND: The purpose of this investigation was to determine the influence of analytical method on reported concentrations of plasma lipids and lipoproteins, and to determine if there are clinical implications of any potential differences on identification of the metabolic syndrome dyslipidemia, CVD risk stratification and classification of LDL subclass phenotype. RESULTS: Plasma triglyceride (TG) concentrations were 1.09 ± 0.06 and 1.17 ± 0.06 mmol/L and plasma high density lipoprotein cholesterol (HDL-C) concentrations were 1.09 ± 0.03 vs 1.19 ± 0.03 mmol/L (both p < 0.05) from 113 duplicate samples sent to two laboratories utilizing different lipid and lipoprotein analytical methods (LABS 1 and 2, respectively). Plasma total cholesterol and low-density lipoprotein cholesterol (LDL-C) concentrations were also significantly different between laboratories. Spearman rho correlations indicate excellent agreement of TG and HDL-C determined by the two laboratories (r = 0.96, TG; r = 0.91, HDL-C, both p < 0.001). Eleven vs. 14 individuals met the TG criteria and 70 vs. 48 met HDL-C metabolic syndrome criteria with LAB 1 and 2, respectively. Apoprotein B concentration (LAB 1) and LDL particle number (LAB 2) were highly correlated. (r = 0.92, P < 0.01). LAB 2 characterized more individuals as LDL pattern B phenotype, as compared to LAB 1 (30 vs. 14%, P < 0.05). CONCLUSION: Different plasma lipid and lipoprotein analytical techniques yield results which are highly correlated, yet significantly different, which suggests a consistent measurement difference. This difference has clinical implications, in that the proportion of individuals identified as meeting the metabolic syndrome dyslipidemia criteria, "at risk" based upon apo B or LDL particle number, and the LDL pattern B phenotype will differ based upon choice of analytical method.