Noninvasive evaluation of NAFLD

A common clinical concern in patients with NAFLD is whether they have NASH or simple steatosis and, more importantly, what the stage of fibrosis is and whether the level of fibrosis has increased over time. Such concern is based on the fact that patients with NAFLD with advanced fibrosis are at greatest risk of developing complications of end-stage liver disease. Although it lacks sensitivity, ultrasonography is an accepted tool for steatosis screening. The controlled attenuation parameter or CAP seems a promising screening technique, but requires further validation. Cytokeratin-18 has been extensively validated, but it is an imperfect serum marker of NASH. Ultrasonography-based transient elastography can exclude advanced fibrosis and cirrhosis, but its main limitation is its reduced applicability in patients with NAFLD, which is not completely solved by use of the XL probe. Of the noninvasive serum markers, the NAFLD fibrosis score is the most validated and has appropriate accuracy in distinguishing patients with and without advanced fibrosis. Although noninvasive methods require further validation, they could be useful for selecting those patients with NAFLD who require a liver biopsy. This Review discusses the advantages and limitations of noninvasive methods for the management of adults with NAFLD, including diagnosis and quantification of steatosis, diagnosis of NASH and staging of hepatic fibrosis.