Noninvasive Assessment of Liver Fibrosis in NAFLD

Nonalcoholic fatty liver disease (NAFLD) has emerged as a leading cause of liver-related morbidity and mortality worldwide, afflicting approximately a billion individuals. NAFLD is a slowly progressive disease that may evolve in a subset of patients toward cirrhosis, hepatocellular carcinoma, and end-stage liver disease. Liver fibrosis severity is the strongest predictor of clinical outcomes. The emergence of effective therapeutics on the horizon highlights the need to identify among patients with NAFLD, those with severe fibrosis or cirrhosis, who are the most at risk of developing complications and target them for therapy. Liver biopsy has been the reference standard for this purpose. However, it is not suitable for large-scale population evaluation, given its well-known limitations (invasiveness, rare but severe complications, and sampling variability). Thus, there have been major efforts to develop simple noninvasive tools that can be used in routine clinical settings and in drug development. Noninvasive approaches are based on the quantification of biomarkers in serum samples or on the measurement of liver stiffness, using either ultrasound- or magnetic resonance-based elastography techniques. This review provides a roadmap for future development and integration of noninvasive tools in clinical practice and in drug development in NAFLD. We discuss herein the principles for their development and validation, their use in clinical practice, including for diagnosis of NAFLD, risk stratification in primary care and hepatology settings, prediction of long-term liver-related and non-liver-related outcomes, monitoring of fibrosis progression and regression, and response to future treatment.