Unicel dxi 800 analyzer

Vitamin B12 levels were measured by competitive-binding immunoenzymatic assays using an Unicel DxI 800 analyzer (Beckman Coulter, Inc., CA). Assay sensitivity was 50 pg/mL, and inter-assay coefficient of variation was <11.4% at serum concentrations of 88 to 975 pg/mL. In this study, biochemical vitamin B12 deficiency was defined as serum B12 <300 pg/mL, not accompanied by serum folic acid deficiency.^{[1 (link),20 (link)]} Based on this distinction, patients were categorized as B12-deficient or normal, and the clinical characteristics of the 2 groups were compared. Serum folic acid deficiency was defined as <4 ng/mL.^{[1 (link)]} Anemia was defined as hemoglobin <13 g/dL for men and <12 g/dL for women, based on the World Health Organization guidelines.^{[21 ]} The homeostasis model of assessment-insulin resistance was calculated using the following equation: fasting glucose (mg/dL) × fasting insulin (μU/mL)/405.^{[22 (link)]} Estimated GFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration criteria. Serum homocysteine levels were measured using the chemiluminescent Microparticle Immuno-Assay (Abbott Architec i2000). Elevated homocysteine was defined as >13.7 μmol/L.^{[8 (link)]} Albuminuria was defined as urine ACR ≥30 mg/gCr.

Traditional cardiometabolic risk factors were determined in serum following standard procedures. ⁷⁶⁷⁷Glucose levels were assessed using an AU5832 analyzer (Beckman Coulter, Brea, CA, USA) with a Beckman Coulter reagent (OSR6521). Insulin was measured by chemiluminescence immunoassays using the UniCel DxI 800 analyzer (Beckman Coulter) with Beckman Coulter chemiluminescent reagents (33410). TC, HDL-C, TG, apolipoproteins A and B, glutamic pyruvic transaminase (GPT), gamma-glutamyl transferase (GGT), and alkaline phosphatase (ALP) were measured using an AU5832 spectrophotometer (Beckman Coulter) with Beckman Coulter reagents (OSR6116, OSR60118, OSR6187, 446410, 447730, OSR6507, OSR6520, and OSR6204). LDL-C (mM) was calculated from the Friedewald formula [ $TC\left(mM\right)-HDLc\left(mM\right)-0·45\times TG\left(mM\right)\text{.}$ C-reactive protein was measured by immunoturbidimetric assays (OSR6299) using an AU5832 spectrophotometer. Leptin and adiponectin were measured in plasma using the MILLIPLEX MAG Human Adipokine Magnetic Bead Panel 2 (Catalog # HADK2MAG-61K) and a MILLIPLEX MAP Human Adipokine Magnetic Bead Panel 1 (Catalog # HADK1MAG-61K), respectively (Luminex Corporation, Austin, TX, USA).
Insulin sensitivity was estimated using the homeostatic model assessment of insulin resistance index (HOMA-IR) calculated as⁷¹ (link): $HOMA-IR=\frac{\text{insulin}\left(\frac{\mathrm{\mu }\text{IU}}{\text{mL}}\right)\ast \text{glucose}\left(\frac{\text{mmol}}{\mathrm{L}}\right)}{22·5}$

Blood samples were obtained, centrifuged to separate the plasma, and stored at −20°C until used in the hormone assay. Plasma concentrations of FSH, LH, T, free T, E2, and SHBG were all tested using a chemiluminescent immunoassay method on the automated UniCel DxI 800 analyzer (Beckman Coulter, Brea, USA). The commercial kits were also provided by Beckman Coulter, Inc. All of the hormone assays were carried out by the same specialized technician, to minimize the effect of between-assay variability.