Advanced MRI measures correlate with histologic steatosis in kids

Last Updated: 2015-02-16

By Larry Hand

NEW YORK (Reuters Health) - Clinicians treating children with nonalcoholic fatty liver disease (NAFLD) may be one step closer to being able to estimate the degree of hepatic steatosis using noninvasive tools.

Researchers in the MRI Rosetta Stone Project found liver proton density fat fraction (PDFF) as measured by magnitude-based magnetic resonance imaging (MRI) correlated with steatosis grade in children.

"The MRI Rosetta Stone Project was a step toward understanding how the MRI measurements relate to the histology measurements," Dr. Jeffrey B. Schwimmer, of Rady Children's Hospital at the University of California, San Diego, told Reuters Health by email.

"Doing so allows for a better understanding of the potential to integrate advanced MRI into clinical protocols for the management of NAFLD in children," he said. "The ability to interpret the meaning of a given MRI-estimated liver PDFF value is essential for the application of MRI as a meaningful longitudinal tool."

The findings were published online February 5 in Hepatology.

Dr. Schwimmer and colleagues enrolled 174 children eight to 17 years old who had undergone the standard liver biopsy for testing for NAFLD. The study population included 24 children whose biopsies showed no steatosis; the remaining children's biopsies showed steatosis grades 1 through 3, with 50 children in each grade.

The researchers scanned the children at 3T using "gradient-recalled-echo technique" that estimates PDFF, then computed PDFF parametric maps using custom-developed software.

The MRI-estimated PDFF values correlated with histologically determined steatosis grade (p<0.01); the correlation was stronger in girls than in boys and weaker in children with 2-4 fibrosis than in those without fibrosis.

For example, the team found that children with low a PDFF (2%) had a 95% chance of having steatosis grade 0, a 5% chance of grade 1 and zero chance of higher grades. Children with a high PDFF (30%) had a zero probability for grade 0 and a 95% probability for grade 2 or 3. Probabilities fluctuated for midrange children.

"As is true for most biomarkers, performance was best in the highest and lowest groups with the greatest amount of noise in the middle," Dr. Schwimmer said. "A priority for future studies should be to improve diagnostic accuracy in the mild to moderate range of steatosis."

The researchers also found that the diagnostic accuracy to distinguish between grades 1 and 2 ranged from 54% to 96%. However, they determined "that no single threshold value has sufficient accuracy to be considered diagnostic for an individual child."

"In order to validate a biomarker for making the diagnosis of NAFLD, it must be shown to reliably and correctly sort each individual child as having or not having NAFLD," Dr. Schwimmer said. "Establishing a biomarker for diagnosis does guarantee that the same biomarker would perform well as a tool to monitor changes in disease status over time."

Any follow-up studies will need to enroll enough girls to see if the difference observed in effect might be due to a smaller number of girls in this study or biology, he said.

"The specific advanced MRI protocol is not currently available on most MRI scanners in the United States," Dr. Schwimmer said. "However, it could be deployed on any modern MRI scanner. We have successfully implemented the protocol on numerous scanners from different manufacturers in ongoing multi-center research."

SOURCE: http://bit.ly/17Cfbb0

Hepatol 2015.