The variability of liver stiffness biomarker quantified by ultrasound (SWE) is equivalent to that of MRI (MR-E). However, the Wilcoxon signed-rank test demonstrated that all variability coefficients computed on liver fat biomarkers were significantly different between MR-PDFF (from ROI1 and ROI2) and US-ATI, on the three different populations: the full cohort, teenagers, or adults only, with higher variability coming from MR-PDFF measurements than US-ATI.

In addition, MR-PDFF were significantly different in adults and teenagers whereas US-ATI variability was not significantly different between populations. The higher MR-PDFF variability observed in teenagers compared to adults could result from higher BMI and breathing artifacts. On the contrary, US-ATI seems to be less sensitive to artifacts as the US-ATI variability coefficients are the same on the two groups. There was no significant difference between VCs from the teenager and adult groups, for stiffness biomarkers (MR-E and SWE).