Variant 2 turbo hemoglobin testing system

Glucose, insulin, and C-peptide concentrations were measured in fasting plasma and at different time points of the OGTT. Blood glucose was measured using The Dimension Vista^® GLU method (REF K1039) (Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA), an adaptation of the hexokinase-glucose-6-phosphate dehydrogenase method [60 ]. Insulin and C-peptide, a marker of insulin secretion, were determined using ADVIA Centaur XPT Immunoassay System test (Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA), a sandwich immunoassay using direct chemiluminescent technology, and specific insulin and C-peptide antibodies. HbA1c was determined using a 2.0 assay on a VARIANT II TURBO Hemoglobin Testing System (Bio-Rad Laboratories Inc., Hercules, CA, USA) using the principle of ion-exchange high-performance liquid chromatography. These analyses were performed at the Research Centre of Laval University Hospital (CHU of Québec) (QC, Canada).
The Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) was used to estimate insulin sensitivity/resistance. HOMA-IR index was calculated according to the following formula: fasting insulin concentration (µL/mL) × fasting glucose concentration (mmol/L)/22.5 [61 (link)].

Peripheral blood samples were collected from each subject and anticoagulated with EDTA-K2. Approximately 2 mL of the anticoagulated blood samples were used for analysis of blood cell parameters on a Sysmex XN-2000 automatic hematology analyzer (Sysmex; Shanghai, China), and the hemoglobin components and levels were analyzed using high-performance liquid chromatography (HPLC) with a VARIANT II TURBO Hemoglobin Testing System (Bio-Rad Laboratories, Inc.; Hercules, CA, USA). Positive thalassemia screening was defined as a mean corpuscular volume (MCV) of <80 fL, a mean corpuscular hemoglobin (MCH) concentration of <27 pg, and/or hemoglobin A2 (HbA2) of >4.0% and/or fetal hemoglobin (HbF) of >2.0% and HbA2 of <2.5%^{1 (link)}. All patients positive for thalassemia screening were subjected to genetic testing of thalassemias.

A questionnaire was administered by research nurses to collect data on socio-demographics, smoking, medical history of HIV, hypertension, tuberculosis (TB), diabetes and their respective drug treatment, and to establish current TB symptomatology. Measurements of brachial blood pressure (BP), weight, height and waist circumference were obtained according to the WHO STEPS (STEPwise Approach to Surveillance) protocol [36 ]. The last two of three BP readings were averaged to estimate the final BP reading. Non-fasting venous blood was collected to measure glycated hemoglobin (HbA1c) using the VARIANT II TURBO Hemoglobin testing system [Bio-Rad, Marnes-la-Coquette, Paris, France] and to test for HIV (Genscreen Ultra HIV Ag-Ab enzyme immunoassay [Bio-Rad]). Participants with a positive HIV immunoassay had reflex measurement of HIV-1 RNA viral load (Abbott RealTime HIV-1 Viral Load [Abbott, IL, USA]) and CD4+ cell count (BD FACS Calibur flow cytometer, BD Bioscience [San Jose, CA, USA]).

Anthropometry was evaluated and laboratory tests were performed in all the participants according to the customary protocol at OPBG. Participants were asked to refrain from intensive physical activity in the 3 days prior to the study. Weight and height were measured using a standard procedure. Up to 3 blood pressure measurements were taken by a physician after a 5 min rest following a standard protocol, and the mean of the 3 measurements was used for the analysis [16 (link)].
After an 8–12 h fast, participants underwent an OGTT (1.75 g/kg body weight up to a maximum of 75 g) with flavored glucose (Glucosio Sclavo Diagnostics, 75 g/150 mL, Sovicille, Italy). Blood glucose was assessed using the glucose oxidase technique (Cobas Integra, Roche, Indianapolis, IN, US); insulin and C-peptide levels were assessed using chemiluminescence on an ADVIA Centaur analyzer (Bayer Diagnostics, Siemens Healthcare, Erlagen, Germany; C-peptide intra- and inter-assay coefficients of variation 3.7–4.1 and 1.0–3.3%, respectively). HbA1c was tested using high-performance liquid chromatography (VARIANT II TURBO Hemoglobin Testing System; Bio Rad, Hercules, CA, USA).

Biochemistry measures were performed at a central laboratory between 2014 and 2017. This included serum total cholesterol, high-density lipoprotein cholesterol (HDL-C), triglycerides (AU5400; Beckman Coulter), and HbA1c (VARIANT II TURBO Hemoglobin Testing System; Bio-Rad). Further details of these measurements and assay performances can be found in the UK Biobank online showcase and protocol.¹²