Diagnostic Modalities for Non-alcoholic Fatty Liver Disease (NAFLD), Non-alcoholic Steatohepatitis (NASH) and Associated Fibrosis

Abstract

NAFLD is a spectrum comprised of isolated steatosis, NASH, advanced fibrosis, and cirrhosis. The majority of NAFLD subjects do not have NASH and don't carry a significant risk for adverse outcomes (cirrhosis and mortality). Globally, the prevalence of NAFLD is approximately 25%. In Asia, a gradient of high prevalence rates to low rates are noted from urban to rural areas. Given the prevalence of NAFLD, the clinical and economic burden of NAFLD and NASH can be substantial. With increasing recognition as an important liver disease, the diagnosis of NASH still requires a liver biopsy which is suboptimal. Although liver biopsy is the most accurate modality to diagnose and stage the severity of NASH, it suffers from being invasive, costly, associated with potential complications, and plagued with interobserver variability of individual pathologic features. A number of non-invasive modalities to diagnose NASH and stage liver fibrosis are being developed. These include predictive models (NAFLD fibrosis score) and serum biomarkers such as Enhanced Liver Fibrosis, (ELF). Other tests are based on radiologic techniques such as transient or MR elastography (MRE) which are used to estimate liver stiffness as a potential surrogate of hepatic fibrosis. Although a dynamic field of research, most of these diagnostic modalities have AUROC between 0.76 to 0.90% with MRE having the best predictive performance. In summary, developing accurate, safe and easily accessible non-invasive modalities to accurately diagnose and monitor NASH and associated fibrosis is of utmost importance in clinical practice and clinical research. These tests are not only important to risk stratify subjects at the greatest risk for progressive liver disease but to serve as appropriate surrogate endpoints for therapeutic clinical trials of NASH.