Measuring liver stiffness using transient elastography in the non-invasive assessment of chronic hepatitis B

Abstract

Liver stiffness measurement using transient elastography has become recently available as a new non-invasive method to assess liver fibrosis in patients with chronic hepatitis B (CHB). The present thesis set out to determine the application of liver stiffness measurement in patients with CHB, including the long-term longitudinal changes and its prognostic value. In a study of 1,268 CHB patients, liver stiffness correlated positively with routine liver biochemistry and hepatitis B virus (HBV) DNA levels, and negatively with albumin and platelet levels. Liver stiffness also correlated well with the different severity of liver diseases. The median liver stiffness in healthy subjects, occult hepatitis B, active hepatitis B, and end-stage cirrhosis were 4.6, 4.2, 8.7, and 33.8 kPa respectively. Using liver stiffness measurement to determine the prevalence of liver fibrosis in 951 CHB patients, 319 (34%) had severe fibrosis, with higher rates seen in older age groups, males, and in patients with higher ALT levels. However, the higher liver stiffness values observed in patients with higher ALT may be secondary to the affect of inflammation rather than fibrosis. A study on 29 patients with severe flare of ALT showed that liver stiffness was increased, with return to near normal levels by 6 months when the ALT levels were normalized. Liver biopsies on a subset of patients showed higher liver stiffness values at the time of flares than expected for the stage of fibrosis seen on histology. However, even mild to moderate elevation of ALT was shown to be associated with higher liver stiffness values independent of underlying liver fibrosis in a study of 38 patients. For long-term prognosis, liver stiffness of ≥10 kPa was associated with a significantly increased risk of subsequent hepatocellular carcinoma development and mortality in 528 HBeAg-negative CHB patients. Longitudinal long-term follow-up also showed significant changes after 3 years in liver stiffness, although this was only observed in specific subsets of patients. In conclusion, liver stiffness measurement with transient elastography is accurate in assessing liver fibrosis in CHB patients, and in determining long-term prognosis. However, elevation of ALT levels can significantly affect liver stiffness.