For a positive diagnosis of NAFLD to be made, there should be

1. Hepatic steatosis by imaging or histology
2. No significant alcohol consumption
3. No competing aetiologies for hepatic steatosis, such as hepatitis C, steatogenic drugs, parenteral nutrition, Wilson’s disease and severe malnutrition
4. No coexisting causes of chronic liver disease, such as hemochromatosis, autoimmune liver disease, chronic viral hepatitis, alpha-1 antitrypsin deficiency, Wilson’s disease and drug-induced liver injury

Once, a diagnosis of NAFLD has been established, patients should be assessed for NASH or fibrosis. While a liver biopsy remains the gold standard to differentiate NAFL from NASH and rule out other chronic liver diseases, elastography and scoring systems based on clinical features and routine biochemical testing can be used to assess fibrosis in patients with NAFLD and thus avoid invasive interventions that can be costly, risky, and potentially painful.

Current guidelines thus recommend that patients suspected of having NASH and/or steatohepatitis should undergo liver biopsy, as non-invasive techniques are expensive have not yet been validated. Biomarkers, fibrosis scores and electrography are recommended as acceptable non-invasive procedures for the identification of cases at low risk of advanced fibrosis/cirrhosis. New metabolomic biomarkers and genetic testing are currently under investigation.