We compared a 4-limb bioelectrical impedance analysis (BIA) system, HBF 359 (Omron), and a 2-limb foot-to-foot device, BC 532 (Tanita), with the standard dual energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) methods for the measurement of body fat percentage (BF), skeletal muscle mass percentage (SMM, or fat-free mass [FFM] for BC 532), and visceral fat level (VF). Body composition was measured in 200 healthy volunteers (100 men and 100 women, mean age 48 years) by HBF 359 and BC 532 and by DXA and MRI. The agreement was assessed by correlation analysis and paired t-test. The correlation coefficients between BIA and DXA or MRI ranged from 0.71 to 0.89 for BF, SMM, and VF by HBF 359 and from 0.77 to 0.90 for BF, FFM, and VF by BC 532 in all subjects and in men and women separately (p < 0.001 for all). Compared with DXA, HBF 359 significantly (p < 0.001) underestimated BF by -5.8% in men and -9.6% in women. Compared with MRI, the corresponding underestimatons (negative) or overestimations (positive) by HBF 359 in men and women were, respectively, +1.9% (p = 0.02) and +1.7% (p = 0.10) for SMM, and +13.3% (p < 0.001) and -8.5% (p = 0.006), for VF. The corresponding values by BC 532 in men and women were -10.7 and -6.2% for BF, -1.4 and -2.5% for FFM, and +20.4 and -18.0% for VF. The BIA devices are accurate in the estimation of body composition, especially skeletal muscle mass or FFM.
N onalcoholic fatty liver disease has a global prevalence of 25% and is defined as the intracellular accumulation of fat in the liver parenchyma exceeding 5% in the absence of competing causes such as chronic viral hepatitis, druginduced steatosis, or other chronic liver diseases such as autoimmune hepatitis, hemochromatosis, or alcohol abuse (1,2). Nonalcoholic fatty liver disease is considered an important cause of chronic liver disease, such as nonalcoholic steatohepatitis and cirrhosis, and even hepatocellular carcinoma (3). People with nonalcoholic fatty liver disease tend to also have obesity, diabetes, dyslipidemia, and hypertension, and are at higher risk of cardiovascular disease (1). Accurate and reliable quantification of liver fat content is critical for the diagnosis, treatment, and monitoring of nonalcoholic fatty liver disease.Liver biopsy has long been the reference standard for assessment of liver fat content, although its application is restricted because of its invasive nature and high cost (4). Noninvasive techniques include US, CT, and MRI. US is an inexpensive and convenient diagnostic tool for nonalcoholic fatty liver disease, but it is semiquantitative and relatively insensitive to individuals with liver fat content less than 20% (5-7). Traditionally, CT was considered accurate for moderate-to-severe steatosis but insensitive to mild steatosis (8,9), and the results are susceptible to variable scanning conditions such as different tube voltages and CT scanners from different manufacturers (9,10). MRI methods, including proton MR spectroscopy and the emerging technique of chemical shift-encoded (CSE) MRI, are regarded as the most accurate noninvasive techniques for the evaluation of liver fat (11)(12)(13)(14)(15). Proton MR spectroscopy and CSE MRI quantify liver fat directly in terms of the proton density fat fraction (PDFF), defined as the ratio of the signal strength from fat to the total signal from fat and water (11,16).
Background: Osteoporosis, obesity, and fatty liver are increasingly common chronic diseases that seriously threaten people's health. Low-dose chest computed tomography (LDCT) scan is frequently used for lung cancer screening in health screenings and checkups. Quantitative computed tomography (QCT) enables the accurate measurement of volumetric bone mineral density (vBMD), liver fat content, and abdominal fat area using the existing LDCT data without extra radiation. We initiated a new project, the China Health Big Data (China Biobank) , which combines the LDCT scan images from lung cancer screening of participants in health checkup with QCT to investigate the added value of QCT to LDCT, in order to establish the normative reference database and diagnosis criteria for the three aforementioned conditions. Methods: The China Biobank project is a prospective nationwide multicenter cohort study that will combine QCT technology with LDCT scans to measure bone mineral density (BMD), intra-abdominal fat distribution, and liver fat content of the generally healthy checkup participants. Mindways QCT calibration phantom (Mindways Software Inc., Austin, TX, USA) and analysis software QCT PRO v6.0 will be used for all centers. Before data collection begins, the European Spine Phantom (ESP) will be used for quality control analysis at each collaborating center. The inclusion criteria are a healthy checkup participant aged 30-90 years, with LDCT as a part of his/her health checkup protocol. Exclusion criteria are pregnant women or participants with a metal implant in the CT scan area. The LDCT images will be transferred to the Mindways workstation for analysis, and vBMD in the L1 and L2 vertebrae, visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and liver fat content will be measured. As part of the health checkup, the demographic, anthropometric parameters, blood pressure, and a routine blood laboratory test will be collected. The estimated sample size will be about 30,000. Results: The combination of QCT with LDCT of the chest is validated in this project. The vBMD of spine, visceral fat and liver fat can be measured with a LDCT chest scan. Conclusions: The China Biobank project will assess the added value of QCT to LDCT, and enable accurate evaluation of the prevalence of osteoporosis, obesity, and fatty liver disease in a very large Chinese cohort.
The relationship between adipose and bone tissues is still being debated. The purpose of our study was to evaluate whether the distribution and volume of abdomen adipose tissue are correlated to trabecular bone mineral density in the lumbar spine. In this cross-sectional study, 320 Chinese women, being divided into two groups according to age ≥55 years and <55 years, were evaluated with quantitative computed tomography (QCT) of the spine to simultaneously evaluate the average trabecular BMD of L2–L4, VAT, and SAT. Possible covariates of height, weight, age, and comorbidities were considered. In the <55-year-old sample, multiple linear regression analyses indicated that VAT volume was negatively correlated to trabecular BMD (P value = 0.0003) and SAT volume had no correlation to trabecular BMD. In contrast, there was no significant correlation between VAT or SAT and BMD in the ≥55-year-old sample. Our results indicate that high VAT volume is associated with low BMD in Chinese women aged <55 years and SAT has no relation with BMD.
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