Body mass index accounts for a 43.7% discordance in fibrosis findings between magnetic resonance elastography (MRE) and transient elastography (TE), according to a study from the University of California, San Diego.

“This study demonstrates that BMI is a significant factor of discordancy between MRE and TE for the stage of significant fibrosis (2-4 vs. 0-1),” wrote Cyrielle Caussy, MD , and her colleagues (Clin Gastrolenterol Hepatol. 2018 Jan 15. doi: 10.1016/j.cgh.2017.10.037). “Furthermore, this study showed that the grade of obesity is also a significant predictor of discordancy between MRE and TE because the discordance rate between MRE and TE increases with the increase in BMI.”

Dr. Caussy of the University of California, San Diego, and her colleagues had noted that MRE and TE had discordant findings in obese patients. To ascertain under what conditions TE and MRE produce the same readings, Dr. Caussy and her associates conducted a cross-sectional study of two cohorts with nonalcoholic fatty liver disease (NAFLD) who underwent contemporaneous MRE, TE, and liver biopsy. TE utilized both M and XL probes during imaging. The training cohort involved 119 adult patients undergoing NAFLD testing from October 2011 through January 2017. The validation cohort, consisting of 75 adults with NAFLD undergoing liver imaging from March 2010 through May 2013, was formed to validate the findings of the training cohort.

The study revealed that BMI was a significant predictor of the difference between MRE and TE results and made it difficult to assess the stage of liver fibrosis (2-4 vs. 0-1). After adjustment for age and sex, BMI accounted for a 5-unit increase of 1.694 (95% confidence interval, 1.145-2.507; P = .008). This was not a static relationship, and as BMI increased, so did the discordance between MRE and TE (P = .0309). Interestingly, the discordance rate was significantly higher in participants with BMIs greater than 35 kg/m2, compared with participants with BMIs below 35 (63.0% vs. 38.0%; P = .022), the investigators reported.

While the study revealed valuable information, it had both strengths and limitations. A strength of the study was the use of two cohorts, specifically the validation cohort. The use of the liver biopsy as a reference, which is the standard for assessing fibrosis, was also a strength of the study. A limitation was that the study was conducted at specialized, tertiary care centers using advanced imaging techniques that may not be available at other clinics. Additionally, the cohorts included a small number of patients with advanced fibrosis.

“The integration of the BMI in the screening strategy for the noninvasive detection of liver fibrosis in NAFLD should be considered, and this parameter would help to determine when MRE is not needed in future guidelines” wrote Dr. Caussy and her associates. “Further cost-effectiveness studies are necessary to evaluate the clinical utility of MRE, TE, and/or liver biopsy to develop optimal screening strategies for diagnosing NAFLD-associated fibrosis.”

Jun Chen, MD, Meng Yin, MD, and Richard L. Ehman, MD, all have intellectual property rights and financial interests in elastography technology. Dr. Ehman also serves as an noncompensated CEO of Resoundant. Claude B. Sirlin, MD, has served as a consultant to Bayer and GE Healthcare. All other authors did not disclose any conflicts.

SOURCE: Caussy C et al. Clin Gastrolenterol Hepatol. 2018 Jan 15. doi: 10.1016/j.cgh.2017.10.037 .