Advanced magnetic resonance imaging (MRI) is showing great promise for the quantitative assessment of hepatic steatosis and may be an important new tool for clinicians in diagnosing and managing nonalcoholic fatty liver disease (NAFLD). Using a new magnitude-based MRI technique, it may be possible to estimate liver proton density fat fraction (PDFF), a biomarker of liver fat content.
“There is a huge unmet need in the approach to diagnosing NAFLD,” said Jeffrey Schwimmer, MD, who is a professor of clinical pediatrics at University of California, San Diego.
A noninvasive method for diagnosing and/or evaluating NAFLD has the potential to impact millions of patients, according to Dr. Schwimmer.
He and his colleagues recently published a study in Hepatology in which they found a strong correlation between the amount of liver fat as measured by the new MRI technique and the grade of liver fat determined by pathology.1
In this study, the researchers compared the MRI technique to the standard liver biopsy in 174 children who were having liver biopsies for clinical care. The mean age of the patients was 14 years. The researchers performed MRI-estimated PDFF and compared the results to the standard pathology liver biopsy.
Results showed that the correlation was influenced by both the patient’s gender and fibrosis stage in the liver. The correlation between the two techniques was strongest in females and in children with minimal scar tissue. The correlation was significantly weaker in children with stages 2 to 4 fibrosis compared with children with no fibrosis or stage 1 fibrosis, Dr. Schwimmer said.
The overall accuracy of predicting the histologic steatosis grade from MRI-estimated liver PDFF was only 56%, and the researchers noted that no single threshold had sufficient sensitivity and specificity to be considered diagnostic for a given patient. However, they concluded that this technique could be used to estimate liver PDFF, and those PDFF values correlate well with steatosis grade by liver histology.
“NAFLD is diagnosed by a combination of history, physical exam, lab testing and liver biopsy,” Dr. Schwimmer said in an interview with Endocrinology Advisor. “There are multiple facets to making the diagnosis of NAFLD, and it is not just knowing that the patient has fat in the liver. A variety of things can cause fatty liver. So, an imaging test like this can help.”
He said although this study was conducted in children, this same technique can be performed in adults, and adult studies are ongoing.
NAFLD is characterized by large droplets of fat in at least 5% of a child’s liver cells, Dr. Schwimmer said. Depending on how the new MRI technology is used, it could have the potential to correctly classify 65% to 90% of children as having or not having fatty liver tissue, according to the researchers.
“We did not set out to try and come up with a test that will replace biopsies,” said Dr. Schwimmer. “The units we use are very different than the language and units used by the pathologists. The MRI is looking at the amount of signal from protons coming from fat molecules relative to the protons coming from water molecules. So it is a ratio. They (pathologists) are not looking at this in the same way. We hope to translate between these two languages.”
Importance of Earlier Detection
The use of MRI for diagnosing and managing patients with NAFLD could potential pick up more patients earlier in the course of the disease. Endocrinologist Philipp Scherer, MD, who is a professor of internal medicine at UT Southwestern Medical Center in Dallas, Texas, said this is more important than ever due to the growing number of NAFLD patients.
“NAFLD is among the most common chronic liver disease in the Western world. Mortality due to liver disease ranks among the top 12 causes of death. Prevalence of NAFLD in the U.S. is close to 20% in the population, so one in five Americans suffers from the disease. As such, NAFLD is rapidly becoming a major issue in the endocrine clinic and continues to be on the rise,” Dr. Scherer told Endocrinology Advisor.
Obesity and diabetes are risk factors for NAFLD. Researchers reported this past November in the journal Radiology that they have found a close association between high-risk coronary artery plaque and NAFLD by using coronary computed tomography angiography (CCTA).2 Lead study author, Stefan Puchner, MD, who is with Massachusetts General Hospital and Harvard Medical School in Boston, said both pathologies can be detected in a single CT examination.