Comparison between the M and XL probes for liver fibrosis assessment by Transient Elastography

Abstract

Objective: Liver stiffness measurement (LSM) using Transient Elastography (TE) for liver fibrosis assessment is difficult to be performed in obese and overweight patients by standard M probe, thus the XL probe was developed. The aim of our paper was to assess the usefulness of the XL probe in daily clinical practice. Material and method: Our study included 216 patients (mean BMI 30.1±4.1 kg/m2) with chronic hepatopathies, in which paired measurements were made using the M (3.5MHz) and XL (2.5 MHz) probes in the same session. In each patient 10 valid LSM were acquired with each probe, a median was calculated, expressed in kiloPascals (kPa). Unreliable TE measurements were considered: fewer than 10 valid shots; with a success rate (SR) <60% and/or interquartile range interval (IQR) ≥30%. Results: In 127 patients reliable LSM could not be obtained by standard M probe, 10 of them normal weight, 25 of them overweight, and 92 obese. By XL probe reliable measurements were obtained in 80/127(63%) of these patients: 8/10 (80%) of the normal weights, 17/25 (68%) of the overweight and 55/92 (59.8%) of the obese. In 98 patients with reliable M probe measurements, XL probe LSMs were also performed. XL LS values strongly and significantly correlated with those obtained by M probe (Spearman r=0.789, p<0.0001), but were significantly lower [median 6.4 kPa (range 3.1-53.8) vs 7.7 kPa (range 3.7-69.1), Wilcoxon paired t test p<0.001)]. Conclusion: By using the XL probe, reliable LSM by TE can be obtained in more than 60% of patients with unreliable measurements by M probe. LSM by XL probe are significantly correlated, but lower, than those obtained by M probe.