Short- and Long-Term Biological Variability of Small Dense LDL, HDL3, and Triglyceride-Rich Lipoprotein Cholesterol.

Background: Measurement of cholesterol within lipoprotein subfractions may aid in cardiovascular disease prediction. Simple, homogenous enzymatic assays for the direct measurement of lipoprotein subfractions have been developed to measure small dense low-density lipoprotein cholesterol (sdLDL-C), high-density lipoprotein-3 cholesterol (HDL3-C), and triglyceride-rich lipoprotein (TRL-C) cholesterol. The objective of this study was to determine biological variability for sdLDL-C, HDL3-C, and TRL-C in a healthy reference population to facilitate interpretation of these analytes.

Estimating short- and long-term reference change values and index of individuality for tests of platelet function.

Background: In order to manage risks of bleeding and thrombosis after some surgical procedures, platelet function is often measured repeatedly over days or weeks using laboratory tests of platelet function. To interpret test results in the perioperative period, it is necessary to understand analytical, biological and between-person variation.

Methods: We collected three separate blood specimens from 16 healthy volunteers on the first study day, and one additional specimen from each volunteer 1, 2, and 3 months later.

Comparing analytical outliers and the percent of emergency department patients with results above the 99th percentile upper reference limit for 2 conventional and one high sensitivity troponin assay.

Objectives: We compared rates of analytical outliers, and percent of emergency department (ED) patients with cardiac troponin (cTn) values above the 99th percentile upper reference limit (URL), for two conventional and one high sensitivity cTn assay.

Methods: We measured 3008 samples from 1931 ED patients by Roche e411 4th generation Troponin T (cTnT); and Abbott STAT Troponin I (cTnI) and high sensitivity troponin I (hscTnI) on an Architect i2000. Within 24h of initial measurement, samples were aliquoted, re-centrifuged, and repeated in duplicate by all methods.