Liver stiffness measurement using XL probe in patients with nonalcoholic fatty liver disease.

Objectives: Liver stiffness measurement (LSM) by transient elastography is a noninvasive test of liver fibrosis, but cannot be performed in a significant proportion of obese patients. The aim of this study was to evaluate the performance of the new XL probe in patients with nonalcoholic fatty liver disease (NAFLD).
Methods: Liver biopsy and paired LSM by both the original M probe and XL probe were performed on 193 consecutive NAFLD patients in France and Hong Kong.
Results: Compared with M probe, XL probe was more likely to achieve 10 valid measurements (95% vs. 81%; P<0.001) and a success rate of over 60% (90% vs. 74%; P<0.001). The areas under receiver operating characteristics curves of XL probe for F2, F3, and F4 disease were 0.80, 0.85, and 0.91, respectively. XL probe tended to generate lower LSM than M probe in the same patient. At a cutoff of 7.2 kPa, the sensitivity, specificity, positive, and negative predictive values for F3 or greater disease were 78%, 78%, 60%, and 89%, respectively. Discordance of at least two stages between XL probe and histology was observed in 16 (9%) patients. Body mass index (BMI) over 35 kg/m(2) was independently associated with discordance (adjusted odds ratio 9.09; 95% confidence interval 1.10-75.43). Reliable measurements by XL probe were obtained in 75% of the overall population and 65% of patients with BMI over 30 kg/m(2).
Conclusions: LSM by XL probe can be performed successfully in most NAFLD patients, but obesity is associated with less accurate and reliable measurements.