MR elastography tops noninvasive staging of liver fibrosis

November 1, 2007

Researchers in Belgium have found that MR elastography is more accurate than a blood test commonly used in the noninvasive staging of liver fibrosis. The study adds weight to clinical literature that suggests MR elastography could replace biopsy.

Researchers in Belgium have found that MR elastography is more accurate than a blood test commonly used in the noninvasive staging of liver fibrosis. The study adds weight to clinical literature that suggests MR elastography could replace biopsy.

Clinical studies show that fibrosis determines the outcome of chronic liver disease and that it can be reversed if treated promptly and at the correct stage. If treated too early, for instance, toxicity and cost may outweigh the benefits.

Hepathologists think that the ideal test should distinguish at least three stages: early, intermediate, and advanced fibrosis. They agree that intermediate fibrosis seems the optimal stage for treatment. Invasive biopsy, the current assessment standard, is not entirely reliable and could lead to complications. Noninvasive techniques, however, such as the aspartate aminotransferase-to-platelet ratio index (APRI) widely available in clinical practice, have not proven their staging efficacy.

MR elastography can accurately identify the stage of fibrosis and should be used to select the right patients for treatment, according to the investigative team led by Dr. Laurent Huwart from the radiology department at the Catholic University of Louvain in Brussels.

Huwart and colleagues enrolled 88 patients with suspected chronic liver disease who underwent MR elastography and APRI exams within two days of liver biopsy. Biopsy-based staging incorporated the METAVIR scoring system designed for patients with hepatitis C, which provides fibrosis scores ranging from F0 (no fibrosis) to F4 (cirrhosis).

The researchers evaluated fibrosis stage assessment for MR elastography and APRI in correlation with the METAVIR system using receiver operating characteristic curve analysis. They found that MR elastography distinguished several stages of fibrosis more accurately than did the APRI blood testing. They published their findings in the November issue of Radiology.

MR elastography scores for fibrosis staging at F2, F3, and F4 were 0.999, 0.997, and 1, respectively. APRI scores for the same stages were, respectively, 0.854, 0.886, and 0.851. The difference was statistically significant for all stage scores (p <0.001; p = 0.003; p = 0.004). The MR elastography procedure comprised 1.5T scanning with a four-element torso coil and a phase-contrast spin-echo sequence through five sagittal sections of the right liver lobe.

The study had some limitations, including the lack of precise correlation between biopsy samples and the viscoelastic maps constructed at MR elastography. Some hepatic vessels may have influenced results as well. The researchers did not study the influence of steatosis, edema, or iron overload on elasticity and viscosity measurements. The relevance of some of these parameters should be further studied in larger series. Study results, however, show that MR elastography is a reliable imaging method that is superior to APRI measurement for the noninvasive staging of liver fibrosis, the researchers said.

"These findings suggest that noninvasive MR elastography potentially has a role in determining the treatment and the prognosis of patients with chronic liver disease because it enables substantial and advanced fibrosis to be readily diagnosed," they said.

For more information from the Diagnostic Imaging archives:

Functional MR imaging techniques vie to replace invasive biopsy

Hardware, software advances give fMRI a place in abdominal imaging

MR elastography expands liver disease imaging