Reliability of liver stiffness measurement in non-alcoholic fatty liver disease: the effects of body mass index.

BACKGROUND: Liver stiffness measurement (LSM) using transient elastography (TE) is used to stage fibrosis in patients with liver disease, diagnostic reliability and the factors affecting its performance in patients with non-alcoholic fatty liver disease (NAFLD) are incompletely understood.

AIM: To assess LSM.

METHODS: Consecutive NAFLD patients (n = 169), assessed by liver biopsy (Kleiner score), anthropometrical, biochemical and metabolic features, underwent LSM using TE with standard M probe.

RESULTS: Liver stiffness measurement was not reliable in 23 patients (14%) due to obesity. Among patients with a reliable TE, a LSM value >7.25 kPa was the best cut-off for predicting significant fibrosis at biopsy (AUC 0.794); however, this cut-off still failed to rule out F2-F4 fibrosis in 31% (false-negative rate) or rule in F3-F4 in 29% (false-positive rate). Similarly a LSM value >8.75 kPa was the best cut-off for severe fibrosis (F3-F4) (AUC 0.870), with a rate of false-negatives 24% and of false-positives 2%. Body mass index was the major determinant of these diagnostic errors in predicting significant and severe fibrosis both by overestimating or underestimating the stage of fibrosis.

CONCLUSIONS: In NAFLD patients, even when liver stiffness measurement is feasible, high BMI values negatively affect the diagnostic reliability. Improved performance of transient elastography could be obtained using specifically designed probes.