Advia 1650 auto analyzer

For the blood tests peripheral venous samples were collected after fasting for at least 8 hours. Total cholesterol, triglyceride (TG), low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma galutamyltransferase (GGT), creatinine, fasting blood glucose, and hemoglobin A1c (HbA1c) were measured. These levels were measured using Bayer Reagent Packs (Bayer HealthCare, Tarrytown, NY, USA) with an automated chemistry analyzer (ADVIA 1650 Autoanalyzer Bayer Diagnostics Leverkusen, Germany). The clinical laboratory has been accredited and participates annually in inspections and surveys done by the Korean Association of Quality Assurance for Clinical Laboratories.

Blood samples were taken from the antecubital vein, collected in serum-separating tube (SST) after at least 10 h of fasting. Serum levels of total cholesterol and triglyceride were determined using an enzymatic colorimetric assay; low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) levels were directly measured using a homogeneous enzymatic colorimetric assay. Serum fasting glucose level was measured using the hexokinase method. Fasting serum glucose, total cholesterol, LDL-C, HDL-C, triglyceride (TG), alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), were measured using Bayer Reagent Packs in an automated chemistry analyzer (Advia 1650 Auto analyzer; Bayer Diagnostics, Leverkusen, Germany). High sensitivity C-reactive protein (hsCRP) was analyzed by particle-enhanced immunonephelometry with the BNII System (Dade Behring, Marburg, Germany). All hematologic measurements were analyzed in one laboratory with the same machines by trained staff using the same methodology throughout. The Korean Society of Laboratory Medicine (KSLM) biannually certified the Laboratory Medicine Department at Kangbuk Samsung Hospital in Seoul, Korea for the Korean Association of Quality Assurance for Clinical Laboratories (KAQACL) and the CAP (Collage of American Pathologists) Proficiency Testing designations.

All participants fasted for at least 14 h before undergoing the blood sampling. Plasma specimens were separated using centrifugation (2,000 rpm for 20 min at 4 °C) and tested immediately. Plasma glucose concentrations were measured using the hexokinase method (ADVIA 1650 Auto Analyzer; Bayer, Leverkusen, Germany), and plasma insulin concentrations were measured using the IRMA test kit (bioSource Europe S.A., Niverlles, Belgium). Fasting concentrations of total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides were measured enzymatically using the Hitachi 747 chemistry analyzer (Hitachi, Tokyo, Japan). Concentrations of HbA1c were evaluated using high-performance liquid chromatography with a Bio-Rad Variant II HbA1c analyzer (Bio-Rad, Montreal, Quebec, Canada). Consenting participants underwent apolipoprotein E genotyping using the methods of Hixson and Vernier^{23 (link)}, and the results were categorized based on the presence or absence of the ε4 allele. HOMA-IR^{24 (link)}, ∆HOMA-IR, ∆HbA1c, and ∆fasting insulin were calculated as: $$\mathrm{HOMA}‐\mathrm{IR}=(\mathrm{fasting}\mathrm{plasma}\mathrm{insulin}[\mathrm{\mu }\mathrm{IU}/\mathrm{mL}]\times \mathrm{fasting}\mathrm{plasma}\mathrm{glucose}\left[\mathrm{mg}/\mathrm{dL}\right]\times 0.0555)/22.5$$ $$\mathrm{\Delta }\mathrm{HOMA}‐\mathrm{IR}=\mathrm{follow}‐\mathrm{up}\mathrm{HOMA}‐\mathrm{IR}-\mathrm{baseline}\mathrm{HOMA}‐\mathrm{IR}$$ $$\mathrm{\Delta }\mathrm{HbA}1\mathrm{c}=\mathrm{follow}‐\mathrm{up}\mathrm{HbA}1\mathrm{c}-\mathrm{baseline}\mathrm{HbA}1\mathrm{c}$$ $$\mathrm{\Delta }\mathrm{fasting}\mathrm{insulin}=\mathrm{follow}‐\mathrm{up}\mathrm{fasting}\mathrm{insulin}-\mathrm{baseline}\mathrm{fasting}\mathrm{insulin}$$