Synchron lx20

The exposure variable was serum sUA. From 1999 to 2001, the sUA levels were measured using Roche Hitachi Model 917 or 704 Multichannel Analyzer, while the Beckman Synchron LX20 was used since 2002 [16 ].
The outcome of interest was blood pressure status measuring by trained research physicians. HTN was defined as self-reported HTN. Subjects with systolic BP ≥ 130 mmHg or diastolic BP ≥ 80 mmHg were considered to have HTN [17 (link)].
Additionally, other covariates included age, sex, race, income-poverty ratio, educational level, body mass index (BMI), diabetes mellitus status, physical activity, smoking behavior, alcohol consumption, total cholesterol, serum homocysteine (Hcy), urine creatinine, blood urea nitrogen, and serum calcium.

A high-sensitivity Near Infrared Particles Immunoassay was used to quantify the concentration of hsCRP from a serum sample of 300 μL. A commercially available device, the SYNCHRON LX-20 (Beckman-Coulter; California, USA), was used to automatically perform the assay. Prior to performing each assay, the SYNCHRON system was calibrated, and a calibration curve was established. The normal reference range for concentrations of hsCRP using this high-sensitivity assay is 0.0–3.3 mg/L [33 (link)].

The exposure variable, TPF, was measured by whole body DXA scan using QDR-4500 Hologic Scanner (Bedford, MA, United States). The outcome variable, SUA, was measured by 704 Multichannel Analyzer or Roche Hitachi Model 917 from 1999 to 2001, Beckman Synchron LX20 from 2002 to 2007, Beckman Coulter UniCel^® DxC800 from 2008 to 2016, and Roche Cobas 6000 (c501 module) in 2017 and 2018.
Other variables included age, sex, race, BMI, ratio of family income to poverty, education level, dietary intakes of energy and nutrients (protein, carbohydrate, and fat), prescription medication use, smoking status (whether smoked at least 100 cigarettes in life), heavy alcohol consumption (ever had 4/5 or more drinks every day), hypertension (mean systolic blood pressure ≥130 mmHg, mean diastolic blood pressure ≥80 mmHg, current use of antihypertensive medications, or self-reported physician-diagnosed hypertension) (19 , 20 (link)), diabetes (self-reported physician-diagnosed diabetes or glycohemoglobin (HbA1c) ≥6.5% in those without a self-reported diagnosis) (21 (link)), weak/failing kidneys (self-reported physician-diagnosed weak/failing kidneys or estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m²) (22 (link)), vigorous work activity and laboratory variables (blood urea nitrogen, cholesterol, triglycerides). These data can be found on the NHANES website.¹

Fasting venous blood samples were collected into silicone test tubes. They were centrifuged upon cooling at 6,000 rpm 430 g for 3 minutes. Then, plasma was refrigerated immediately and stored at a temperature no higher than -35 ^ºС until they were analysed. Samples were processed according to the recommendations of the manufacturer of the analytical technique. SUA level was measured by enzymatic methods using a chemical analyzer Beckman (Synchron LX20, city, state). Analytical range average for SUA was 0.5-82 mmol/L. N-terminal pro-brain natriuretic peptide (NT-pro-BNP) was measured by immune-electro-chemiluminescence method using sets by R&D Systems (city, state, USA) on Elecsys 1010 analyzer (Roche, Mannheim, Germany). Calibration of the assay was performed according to the manufacturer’s recommendations and values were normalized to a standard curve. Concentrations of total cholesterol (TC) and high-density lipoprotein (HDL) cholesterol were determined with Dimension Clinical Chemistry System^® (Dade Behring Inc, Newark, NJ). Low-density lipoprotein (LDL) cholesterol was calculated using Friedewald formula.^{20 (link)}