How to Diagnose Nonalcoholic Fatty Liver Disease

Patients with nonalcoholic fatty liver disease (NAFLD) are asymptomatic and present with either unexplained abnormal liver blood tests or a bright liver on ultrasonography. Some patients will have normal liver blood tests raising the issue of whether patients with risk factors for NAFLD (diabetes and/or metabolic syndrome [MS]) should be screened for its presence with biomarkers, such as the fatty liver index (FLI). The diagnosis of NAFLD requires the exclusion of other causes of chronic liver disease and steatosis, especially heavy alcohol consumption and viral hepatitis particularly HCV genotype 3. Diagnostic work-up should include evaluation of family and personal history of components of the MS and assessment of liver tests, fasting blood glucose, triglycerides and HDL levels. A drug history is important due to a number being associated with steatosis. To confirm the diagnosis of NAFLD and quantify steatosis, ultrasound (US) and MRI-based techniques are available but none are in routine use outside clinical trials. Standard US is no more accurate than biomarkers such as FLI. The accurate staging of NAFLD requires liver biopsy; however, this is clearly impractical for such a prevalent disease. Accordingly, a number of imaging and blood-based biomarker tests have been evaluated. While none have proved reliable for the diagnosis of nonalcoholic steatohepatitis, several have proved accurate in diagnosing the presence of stage 3 or 4 fibrosis, including the NAFLD fibrosis score, fibrosis-4 and the enhanced liver fibrosis test. Of the imaging techniques, elastography has received the most attention and is being used in routine clinical practice. US acoustic radiation force impulse imaging, and MR-based elastography have recently been described but none are sufficiently accurate to replace liver biopsy for clinical trials as yet or are cost effective for use in routine clinical settings.