Fat and Fiber: How the Controlled Attenuation Parameter Complements Noninvasive Assessment of Liver Fibrosis
Fat and Fiber: How the Controlled Attenuation Parameter Complements Noninvasive Assessment of Liver Fibrosis
复制标题
脂肪和纤维：受控衰减参数如何补充肝纤维化的无创评估
DOI：
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发表时间：
2014
影响因子：
3.1
通讯作者：
V. Wong
中科院分区：
文献类型：
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作者：
G. Wong;V. Wong
非酒精性脂肪性肝病（NAFLD）是发达国家和发展中国家日益严重的问题，影响15- 40%的人口[1]。NAFLD曾被视为良性疾病，是隐源性肝硬化和隐源性肝细胞癌（HCC）的主要原因[2]，也是肝移植的第三大最常见适应症[3]。管理NAFLD的临床医生面临的一个关键挑战是建立诊断并区分单纯脂肪变性和晚期疾病[4]。此外，脂肪变性通常与其他慢性肝病共存，如慢性丙型肝炎[5]。经腹超声检查（USG）是诊断肝脂肪变性最常用的成像工具，但只有当脂肪浸润量超过33%时才有信心[6]。尽管质子磁共振波谱（H-MRS）是一种准确且可重复的无创性肝脏脂肪定量方法，但其在许多领域的可用性有限[1]。最初开发用于诊断肝纤维化和肝硬化的瞬时弹性成像（Fibroscan，Echosens，巴黎，法国）已在NAFLD患者中得到验证[7]。Fibroscan采用的基本技术涉及通过肝脏组织传播的塑性剪切波，结合用于跟踪和测量剪切波传播速度的脉冲回波超声，剪切波传播速度与组织硬度直接相关，因此与肝纤维化的严重程度直接相关[8]。其最新迭代包括受控衰减参数（CAP）的测量，即使用Fibroscan常规M探头采集的信号测量3.5 MHz的前向和返回超声信号的衰减。在给定频率下，超声衰减系数可以用dB/m表示。由于超声信号在脂肪中的衰减大于在水中的衰减，因此CAP可用于估计肝脏脂肪变性的程度[9]。CAP的诊断吸引力在于它可以使用能够同时评估肝脂肪变性和纤维化的相同仪器与肝硬度同时测量[8]。关于CAP诊断不同程度肝脂肪变性的准确性的数据正在不断发展。在一项混合病因慢性肝病患者的回顾性队列中，CAP有效检测到低度脂肪变性（[10%]），在临界值238 dB/m时，灵敏度为91%，特异性为81%[9]。CAP的准确性在两项混合病因肝病[10，11]和单一病因人群（包括慢性B肝炎（CHB）、慢性丙型肝炎、NAFLD和酒精性肝病[12]）的前瞻性研究中得到证实。表1总结了不同程度脂肪变性的建议诊断性能和临界值。然而，关于其在健康受试者和CHB患者中的性能的数据要么缺乏要么不足。在本期的《消化系统疾病与科学》中，两组研究人员提供了重要的数据来说明CAP在这两种情况下的准确性。Chon等人[16]报告了来自264名健康受试者的CAP数据，这些受试者要么是潜在的肝脏供体，要么是接受常规G. L- H.黄（&）V.W. - S.香港中文大学消化疾病研究所，中国香港特别行政区沙田，电子邮件：wonglaihung@cuhk.edu.hk
Nonalcoholic fatty liver disease (NAFLD) is an evergrowing problem in the developed and developing worlds, affecting 15–40 % of the population [1]. Once regarded as a benign condition, NAFLD is the leading cause of cryptogenic cirrhosis and cryptogenic hepatocellular carcinoma (HCC) [2], and the third most frequent indication for liver transplantation [3]. A key challenge faced by clinicians who manage NAFLD is to establish the diagnosis and to differentiate simple steatosis from advanced disease [4]. Furthermore, steatosis often coexists in other chronic liver diseases such as chronic hepatitis C [5]. Trans-abdominal ultrasonography (USG) is the commonest imaging tool used in the diagnosis of hepatic steatosis, but only with confidence when the amount of fatty infiltration exceeds 33 % [6]. Although proton magnetic resonance spectroscopy (H-MRS) is an accurate and reproducible noninvasive means of quantifying hepatic fat, its availability is limited in many areas [1]. Transient elastography (Fibroscan, Echosens, Paris, France), originally developed for the diagnosis of liver fibrosis and cirrhosis, has been validated in patients with NAFLD [7]. The fundamental technology employed by Fibroscan involves a plastic shear wave that propagates through liver tissue combined with a pulse-echo ultrasound used to follow and measure the velocity of the propagation of the shear wave, which is directly related to tissue stiffness and hence severity of liver fibrosis [8]. Its latest iteration includes the measurement of the controlled attenuation parameter (CAP), a measurement of the attenuation of the forward and return ultrasound signal at 3.5 MHz using signals acquired by the regular M probe of Fibroscan. At a given frequency, the ultrasound-attenuation coefficient can be expressed in dB/m. Since the attenuation of ultrasound signals is greater in fat than in water, CAP may be used to estimate the degree of hepatic steatosis [9]. The diagnostic attractiveness of CAP is that it may be measured concurrently with liver stiffness using the same instrument enabling the simultaneous assessment of hepatic steatosis and fibrosis [8]. Data concerning the accuracy of CAP to diagnosis different degrees of hepatic steatosis are evolving. CAP efficiently detected low-grade steatosis ([10 %), with a sensitivity of 91 % and specificity of 81 % at a cutoff value of 238 dB/m in a retrospective cohort of patients of mixed etiology chronic liver diseases [9]. The accuracy of CAP was confirmed in two prospective studies of mixed etiology liver disease [10, 11], and in single etiology populations, including chronic hepatitis B (CHB), chronic hepatitis C, NAFLD, and alcoholic liver disease [12]. The suggested diagnostic performance and cutoff values for different degrees of steatosis are summarized in Table 1. Nonetheless, data concerning its performance in healthy subjects and patients with CHB were either lacking or insufficient. In this issue of the Digestive Diseases and Sciences, two groups of investigators provide important data to illustrate the accuracy of CAP in these two settings. Chon et al. [16] report CAP data from 264 healthy subjects, either as potential liver donors or in subjects undergoing routine G. L.-H. Wong (&) V. W.-S. Wong Institute of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China e-mail: wonglaihung@cuhk.edu.hk
影响因子：
29.4
作者：
Charlton, Michael R.;Burns, Justin M.;Dierkhising, Ross A.
通讯作者：
Dierkhising, Ross A.