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Reply to “Multiparametric MRI in patients with nonalcoholic fatty liver disease”

We read with interest the article “Multiparametric MRI in patients with nonalcoholic fatty liver disease” by Schaapman et al. published recently in JMRI. The spectrum of conditions known as nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) are a focus of intense interest in the scientific and clinical community due to the growing health and economic burden that they pose. While the stated goal of the review article is welcome, we believe that some statements in the article are not supported in the literature. Specifically, the review article asserts that T1 mapping (specifically a proprietary version that has been corrected for accelerated R2* relaxation due to liver iron content, referred to as “cT1”) “can be used to assess liver tissue composition for the extent of fibrosis and inflammation.” While one early study showed modest correlation with fibrosis stage in NAFLD patients, there has since been a growing body of evidence that shows poor correlation between liver fibrosis severity and “cT1.” This is actually evident in the primary piece of evidence that the authors quote in reference to the technique. That study revealed that “cT1 showed no significant trend across the fibrosis stages (p = 0.068).” The referenced study also showed that “cT1” had only modest diagnostic performance for distinguishing simple steatosis from the inflammatory activity of NASH (area under receiver operator characteristic curve, AUROC: 0.69). Other studies continue to show that “cT1”/T1 mapping has poor diagnostic performance for predicting liver fibrosis, or only marginal additive value to magnetic resonance elastography (MRE) and proton density fat fraction (PDFF) for NAFLD/NASH evaluation. Despite the diversity of histopathologic findings in NAFLD/ NASH, it is important to keep in mind that only liver fibrosis stage (as opposed to degree of steatosis or inflammation) has been shown to correlate strongly with liver disease mortality. The evidence cited in this article does not show that “cT1” is suitable for assessing fibrosis. Given the escalating importance of NAFLD and NASH as a global health concern, there is a strong need to maintain clarity in the reviews of the biomarker literature. There is little doubt that MRI has an important role in management of NAFLD and NASH. PDFF and MRE represent two techniques that have a large body of evidence supporting their use to answer specific questions about the state of histopathology in NAFLD and NASH. However, based on the evidence cited in this review it is not clear what role T1 and/or “cT1” may play in the management of NAFLD and NASH.