Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong; State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong, Hong Kong.
Sezione di Gastroenterologia, Di.Bi.M.I.S., University of Palermo, Palermo, Italy.
J Hepatol. 2017 Sep;67(3):577-584. doi: 10.1016/j.jhep.2017.05.005. Epub 2017 May 12.
BACKGROUND & AIMS: Controlled attenuation parameter (CAP) can be performed together with liver stiffness measurement (LSM) by transient elastography (TE) and is often used to diagnose fatty liver. We aimed to define the validity criteria of CAP.
CAP was measured by the M probe prior to liver biopsy in 754 consecutive patients with different liver diseases at three centers in Europe and Hong Kong (derivation cohort, n=340; validation cohort, n=414; 101 chronic hepatitis B, 154 chronic hepatitis C, 349 non-alcoholic fatty liver disease, 37 autoimmune hepatitis, 49 cholestatic liver disease, 64 others; 277 F3-4; age 52±14; body mass index 27.2±5.3kg/m). The primary outcome was the diagnosis of fatty liver, defined as steatosis involving ≥5% of hepatocytes.
The area under the receiver-operating characteristics curve (AUROC) for CAP diagnosis of fatty liver was 0.85 (95% CI 0.82-0.88). The interquartile range (IQR) of CAP had a negative correlation with CAP (r=-0.32, p<0.001), suggesting the IQR-to-median ratio of CAP would be an inappropriate validity parameter. In the derivation cohort, the IQR of CAP was associated with the accuracy of CAP (AUROC 0.86, 0.89 and 0.76 in patients with IQR of CAP <20 [15% of patients], 20-39 [51%], and ≥40dB/m [33%], respectively). Likewise, the AUROC of CAP in the validation cohort was 0.90 and 0.77 in patients with IQR of CAP <40 and ≥40dB/m, respectively (p=0.004). The accuracy of CAP in detecting grade 2 and 3 steatosis was lower among patients with body mass index ≥30kg/m and F3-4 fibrosis.
The validity of CAP for the diagnosis of fatty liver is lower if the IQR of CAP is ≥40dB/m. Lay summary: Controlled attenuation parameter (CAP) is measured by transient elastography (TE) for the detection of fatty liver. In this large study, using liver biopsy as a reference, we show that the variability of CAP measurements based on its interquartile range can reflect the accuracy of fatty liver diagnosis. In contrast, other clinical factors such as adiposity and liver enzyme levels do not affect the performance of CAP.
受控衰减参数（CAP）可通过瞬时弹性成像（TE）与肝硬度测量（LSM）联合进行，常用于诊断脂肪肝。本研究旨在确定 CAP 的有效性标准。
在三个欧洲和香港的中心，对 754 例不同肝病患者（推导队列，n=340；验证队列，n=414；101 例慢性乙型肝炎，154 例慢性丙型肝炎，349 例非酒精性脂肪性肝病，37 例自身免疫性肝炎，49 例胆汁淤积性肝病，64 例其他；277 例 F3-4；年龄 52±14 岁；体重指数 27.2±5.3kg/m²）进行了肝活检前的 M 探头 CAP 测量。主要结局是脂肪肝的诊断，定义为肝内 5%以上的肝细胞发生脂肪变性。
CAP 诊断脂肪肝的受试者工作特征曲线（ROC）下面积（AUROC）为 0.85（95%置信区间 0.82-0.88）。CAP 的四分位间距（IQR）与 CAP 呈负相关（r=-0.32，p<0.001），提示 CAP 的 IQR 与中位数的比值可能不是一个合适的有效性参数。在推导队列中，CAP 的 IQR 与 CAP 的准确性相关（CAP 的 AUROC 分别为 IQR of CAP <20[15%的患者]、20-39[51%]和≥40dB/m[33%]的患者为 0.86、0.89 和 0.76）。同样，验证队列中 CAP 的 AUROC 分别为 IQR of CAP <40 和≥40dB/m 的患者为 0.90 和 0.77（p=0.004）。在 BMI≥30kg/m²和 F3-4 纤维化的患者中，CAP 检测 2 级和 3 级脂肪变性的准确性较低。
如果 CAP 的 IQR≥40dB/m，则 CAP 诊断脂肪肝的有效性较低。
CAP 是通过瞬时弹性成像（TE）来检测脂肪肝的。在这项大型研究中，我们以肝活检为参考，表明基于 CAP 四分位间距的测量值变化可以反映脂肪肝诊断的准确性。相比之下，其他临床因素，如肥胖和肝酶水平，并不影响 CAP 的性能。
