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MRI-PDFF suboptimal in identifying advanced NASH, fibrosis

Results of a study on liver histology features in patients with nonalcoholic fatty liver disease and nonalcoholic steatohepatitis revealed that magnetic resonance imaging-estimated proton density fat fraction was suboptimal in identifying patients with advanced NASH or fibrosis.

“While MRI-PDFF is a useful tool for the non-invasive detection of NAFLD and quantification of steatosis, we found that PDFF was not accurate enough to distinguish between NAFLD, NASH with early fibrosis, and NASH with advanced fibrosis in individual patients,” Benjamin Wildman-Tobriner, MD, from Duke University Medical Center in North Carolina, and colleagues wrote.

The retrospective study comprised 370 patients with NAFLD or NASH. At baseline, PDFF values correlated significantly with positive readings for steatosis grade (r = 0.78; P < .001) and NASH activity score (r = 0.54; P < .001), and with negative readings for fibrosis stage (r = –0.59; P < .001).

However, the researchers observed a substantial overlap between PDFF values for low and high NASH activity score and between PDFF values for early and advanced fibrosis stages.

“When different PDFF value thresholds were applied to the study population, progressively larger numbers of subjects were excluded as threshold values increased.” Wildman-Tobriner and colleagues wrote.

For NASH activity score of 4 or higher, the optimal PDFF threshold was 12.4% with a sensitivity and specificity of 0.75. Positive predictive value was 0.13 and negative predictive value was 0.98.

For fibrosis stage 3 or higher, the optimal PDFF threshold was 20.4% with a sensitivity of 0.53 and specificity of 0.17. Positive predictive value was 0.63 and negative predictive value was 0.14.

“PDFF does not appear to be a strong predictor of advanced liver fibrosis or NASH for an individual patient, but may be more useful for risk stratification,” the researchers wrote. “Our data suggest that at the time of diagnosis, a patient with high liver fat content may or may not have NASH. These results suggest that for optimal patient management, techniques other than (or combined with) MRI-PDFF such as ultrasound- or MRI-based elastography or liver biopsy remain necessary for assessing hepatic parenchymal changes other than steatosis.” – by Talitha Bennett

Disclosure: Wildman-Tobriner reports no relevant financial disclosures. Please see the full study for the other authors' relevant financial disclosures.