Non-invasive assessment of liver fibrosis with transient elastography (FibroScan®): applying the cut-offs of M probe to XL probe

Background and rationale for the study. Limited studies have aimed to define the cut-offs of XL probe (XL cut-offs) for different stages of liver fibrosis, whereas those of M probe (M cut-offs) may not be applicable to XL probe. We aimed to derive appropriate XL cut-offs in overweight patients. Patients with liver stiffness measurement (LSM) by both probes were recruited. XL cut-offs probe for corresponding M cut-offs were derived from an exploratory cohort, and subsequently validated in a subgroup patients also underwent liver biopsy. The diagnostic accuracy of XL cut-offs to diagnose advanced fibrosis was evaluated. Results. Total 517 patients (63% male, mean age 58) who had reliable LSM by both probes were included in the exploratory cohort. There was a strong correlation between the LSM by M probe (LSM-M) and LSM by XL probe (LSM-XL) (r(2) = 0.89, p < 0.001). A decision tree using LSM-XL was learnt to predict the 3 categories of LSM-M (< 6.0kPa, 6.0-11.9kPa and >= 12.0kPa), and XL cut-offs at 4.8kPa and 10.7kPa were identified. These cut-offs were subsequently validated in a cohort of 147 patients who underwent liver biopsy. The overall accuracy was 89% among 62 patients whose LSM-XL < 4.8kPa or >= 10.7kPa. These cut-offs would have avoided under-staging of fibrosis among patients with body mass index (BMI) > 25-30 kg/m(2) but not > 30 kg/m(2). Conclusions. XL cut-offs at 4.8kPa and 10.7kPa were the best estimates of 6.0kPa and 12.0kPa of M probe for patients with BMI > 25-30 kg/m(2). Patients with BMI > 30 kg/m(2) might use M probe cut-offs for XL probe.