Comparison of 2-D Shear Wave Elastography and Transient Elastography for Assessing Liver Fibrosis in Chronic Hepatitis B

Abstract

This study compared 2-D shear wave elastography (SWE) and transient elastography (TE) for liver fibrosis staging in patients with chronic hepatitis B (CHB) infection using liver biopsy as the reference standard. Patients with CHB infection who underwent liver biopsy were consecutively included. After exclusions, 257 patients were analyzed. Two-dimensional SWE resulted in a significantly higher rate of reliable measurements (98.1%, 252/257) than TE (93.0%, 239/257) (p = 0.011). Liver stiffness measurements of the two examinations exhibited a strong correlation (r = 0.835, p < 0.001). In patients given a confirmed histologic diagnosis, Spearman's rank coefficients were 0.520 in stage F0 (p < 0.001), 0.684 in stage F1 (p < 0.001), 0.777 in stage F2 (p < 0.001), 0.672 in stage F3 (p < 0.001) and 0.755 in stage F4 (p < 0.001). There were no significant differences between the areas under the receiver operating characteristic (ROC) curves of 2-D SWE and TE for liver fibrosis staging (all p values > 0.05). Two-dimensional SWE had diagnostic accuracy comparable to that of TE for liver fibrosis staging. The measurements that the two techniques provide are not interchangeable.

Introduction

In patients with chronic hepatitis B (CHB) infection, evaluating the degree of liver fibrosis is important in determining their medical management and prognosis. As fibrosis progresses, there is increasing portal hypertension, loss of liver function and a higher risk of hepatocellular carcinoma. Liver biopsy (LB) is still considered the reference standard in the evaluation of liver fibrosis (Bravo et al. 2001). However, LB is an invasive procedure and may occasionally cause severe complications, limiting its use for screening and frequent follow-up (Yoshioka and Hashimoto, 2012). Tracking not only the progression, but also the regression of liver fibrosis over time could be of clinical significance. Therefore, considerable effort has been extended to develop non-invasive methods for the staging of liver fibrosis.

Transient elastography (TE) is a non-invasive method for staging liver fibrosis that evaluates liver stiffness by measuring the velocity of shear waves in the liver parenchyma generated by a mechanical push. TE is the oldest and most validated elastographic method used to assess liver fibrosis and has been recommended as a non-invasive method for the staging of hepatic fibrosis by the clinical practice guidelines of the European Association for the Study of the Liver 2012 (Myers et al., 2012, Trembling et al., 2014). However, TE can be difficult in obese patients or those with a narrow intercostal space and cannot technically be performed in patients with ascites (Cosgrove et al. 2013).

Two-dimensional shear wave elastography (2-D SWE) is a newer ultrasound elastography technique based on shear waves that is available on a clinical diagnostic ultrasound scanner (Muller et al. 2009). Like TE, 2-D SWE can measure liver stiffness based on shear wave velocity estimation, which is used to calculate Young's modulus (Bamber et al. 2013). Unlike TE, 2-D SWE can be conveniently performed using a conventional ultrasound scanner and can create a real-time, 2-D quantitative map of liver tissue stiffness under the guidance of very high frame rate B-mode imaging (Shiina et al. 2015). Two-dimensional SWE has proven to be a reliable method for the non-invasive evaluation of liver stiffness (Ferraioli et al., 2012, Ferraioli et al., 2015, Gerber et al., 2015, Hudson et al., 2013, Woo et al., 2015). Mutual validation or interchangeability among the two ultrasound elastography techniques may be important for patient care because different imaging techniques are frequently used to monitor disease progression in patients with chronic liver disease, and the results of both techniques can be expressed in kilopascals. Most published studies concerning the use of TE and other ultrasound elastographic techniques have focused on hepatitis C virus-related fibrosis. There have been few published studies comparing 2-D SWE and TE in the assessment of liver fibrosis with histologic confirmation in patients with CHB infection (Leung et al., 2013, Zeng et al., 2014).

Therefore, the goal of this study was to compare 2-D SWE and TE for liver fibrosis staging in the same individuals with CHB infection, considering liver biopsy as the reference standard.