Quantitative Evaluation Of Visceral Fat In Abdominal Obesity And Its Clinical Application

Abdominal visceral fat accumulation was the most important pathophysiological characteristics of metabolic syndrome (MS)[1-7]. Abdominal obesity was commonly diagnosed in clinical by methods of measuring waist circumference (WC) and waist-hip ratio (WHR). The other ways which could quantitative analysis of the amount of body fat were: bioelectrical impedance analysis (BIA), ultrasonography examination, dual-energy X-ray absorptiometry (DEXA), computed tomography (CT), magnetic resonance imaging (MRI) and so on. The above methods had certain advantages and disadvantages. WC and WHR were simple, but could not predict abdominal fat distribution quantitatively. BIA reflected only total body fat. DEXA could not measure the local body fat. Ultrasonography showed the local adipose tissue cross-section of the image feature, and had a better correlation with CT [8-10]. The CT and MRI were the current gold standard methods of quantitative determinating visceral fat distribution [11,12], but there were high cost of detection and certain radioactive.In recent years, studies had shown that fat accumulation might release a variety of cells inflammatory cytokines, adipocytokines and vasoactive peptides, leading to insulin resistance and damage of heart, kidney and vascular[13]. Therefore, whether existing of visceral fat accumulation in determining the type of abdominal obesity, assessing their metabolic cardiovascular risk and guiding therapy was important. Although there were a small amount of reports about quantitative analysis of abdominal with MRI, CT and Ultrasonography [14-16], but which with not comparison between the methods. In addition, because there were limitations in clinical application of MRI and CT, it was very necessary to establish a simple and reliable quantitative evaluation method of visceral fat.ObjectiveTo compare the measurements of obesity, including body mass index(BMI), WC, WHR, BIA, ultrasonography and CT, in predicting the quantification of visceral adipose in abdominal obesity, evaluate the best cut-off point, sensitivity and specificity of these methods, and discuss the determination of which obesity type it was with WC, BIA and ultrasonography.MethodsAll the subjects (2155 cases of men, 2146 cases of women) received examination of height, weight, WC and hip circumference. Of 4301 subjects, 3458 subjects received examination of BIA, 2553 subjects received examination of ultrasonography, 1039 subjects received examination of CT and 659 cases with the above-mentioned three kinds of examination.(1) Height, weight, WC and hip circumference (H) were measured with the method which WHO recommended[17]. All measurements were finished by the same staff. Each consecutive measurement took 3 times on average.(2) TANITA model TBF-300 body fat analyzer (TANITA Corporation), calculation of body fat content (FAT%), body fat weight (Fatmass) by measurement of lower extremity impedance, combined with height, weight, age, gender and other parameters.(3) HY260L B-type ultrasonic diagnostic apparatus, 3.5MHz probe for measurement of subcutaneous fat thickness (A), 7.4MHz probe measurement for visceral fat thickness (B). All ultrasound measurements were finished by the same staff. Each consecutive measurement took 3 times on average.(4) Some of the patients in the fasting state scanned on abdomen by spiral CT. The patient supined and held on breath in the scanning process. Umbilical plane (L4 ~ L5 segment) was for the scanning level. With the software on CT we calculated visceral fat area (VA) and subcutaneous fat area (SA) on the umbilical layer images.(5)①VFO Diagnosis: visceral fat area measured by CT≥100cm2 as the diagnostic criteria to determine VFO[11,12];②SPSS 13.0 statistical analysis software was for analysis. Receiver operating characteristic (ROC) curve was used as index for analysising parameters of BMI, WC, WHR, BIA, ultrasound measurements to determine the best cut-off point VFO and its sensitivity and specificity.Result(1) It was accurate for WC, Fatmass, BMI, B, FAT% and WHR(AUCROC: 0.730～0.867) to diagnosis visceral fat obesity. (2) The best cut-off points, sensitivity and specificity of these methods in predicting abdominal visceral obesity in male and female were as follow: WC: 89.5cm(76.5%,70.6%), 85.5cm(87.6%,66%). BMI: 25kg/m2(80.0%,65.6%), 26kg/m2(73.2%,71.6%). WHR: 0.97(63.5%,76.7%), 0.95(56.7%,78.9%). FAT%: 29%(61.2%,75.5%), 38%(68.0%,70.1%). fatmass: 18.6kg(78.2%,66.3%), 20.4kg(84.5%,55.7%). B: 38.5mm(73.5%,70.6%), 34.7mm(71.1%,80.9%).ConclusionWC, fatmass, BMI, B, FAT% and WHR all can predict visceral adipose in abdominal obesity, in which WC is the best. For a given WC, we can determine the type of obesity by BIA and US.