Transient elastography in patients with non-alcoholic fatty liver disease (NAFLD)

2007 Gut 56, 9 (1330-1331)

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver injury in many countries around the world [1]. NAFLD covers a wide spectrum, ranging from simple steatosis, which is generally non-progressive, to nonalcoholic steatohepatitis (NASH). There are no established noninvasive methods of evaluation for patients with NASH, and until recently liver biopsy was the only method of evaluating liver fibrosis. Transient elastography is a new technique that allows rapid, noninvasive measurement of mean tissue stiffness, and has been demonstrated to be useful for accurately estimating hepatic fibrosis in patients with chronic hepatitis C [2]. The
purpose of this study was to determine the usefulness of liver stiffness measurement (LSM) with the new medical device called Fibroscan (EchoSens, Paris, France), based on ultrasound transient elastography, in patients with NAFLD. We performed LSMs in 67 NAFLD patients (age: 50.4 + 13.3) in whom the diagnosis had been confirmed by liver biopsy and the severity of fibrosis had been scored according to the method of Brunt [3]. Box plots were prepared to show the elasticity measurements according to the stage of histological fibrosis (Figure 1). The median liver stiffness values (and 95 % CI) were F 0, 4.907 (4.417 – 5.396) kilo Pascal (KPa); F 1, 6.142 (5.582 – 6.702) KPa; F2, 7.894 (6.384 – 9.404) KPa; F3, 11.027 (8.555 – 13.500) kPa; F4, 26.960 (17.705 –36.215) KPa. The results of the analysis revealed stepwise increases in liver stiffness with increasing histological severity of hepatic fibrosis (p < 0.0001 by Kruskal-Wallis test). The areas under the receiver-operating characteristics (AUROC) curves, which estimate the diagnostic performance of the elasticity measurements for hepatic fibrosis stage equal to or greater than F 1, F 2, F 3, and F 4, were 0.881, 0.876, 0.914, and 0.997
respectively. Table 1 shows the optimal liver stiffness cutoff values for NAFLD patients, and sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) were calculated. The results of this study demonstrated a significant positive correlation between liver stiffness and the severity of liver fibrosis in patients with NAFLD. Rapid, noninvasive estimation of the stage of fibrosis in NAFLD patients, especially NASH patients is of major clinical interest, because they have been shown to be at a high risk of developing complications, such as portal hypertension or hepatocellular carcinoma, and therefore require close follow-up. On the other hand, liver tissue containing fat deposition is presumably softer than healthy liver parenchyma, and sound velocity has been reported to decrease as fatty liver progressed in an animal experiment. However, the results of the present study also confirmed that the correlation between liver stiffness and severity of fibrosis is unaffected by the grade of activity or degree of steatosis [4]. The results demonstrated LSMs are very useful means of estimating the severity of hepatic fibrosis in NAFLD patients. This is the first study to demonstrate a consistent and major increase in liver stiffness in NASH patients, as confirmed by the results of liver biopsy, which remains the gold standard for evaluation of the severity of liver fibrosis in NASH patients. LSM is a noninvasive, clinically useful method of estimating the severity of liver fibrosis in NASH patients.

Pubmed : 17470477