Comparison between the M and XL probes for liver fibrosis assessment by transient elastography.

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.