A Disease Severity Index (DSI) is provided for assessment of chronic liver disease in a patient using non-invasive liver function test results. A DSI was derived from non-invasive liver function test results based on hepatic blood flow. The DSI is used in methods for prediction of clinical outcomes, prediction of response to antiviral treatment, and assessment of progression of chronic liver diseases. Non-invasive methods to diagnose three distinct categories of patients with Primary Sclerosing Cholangitis (PSC) are provided. The methods can be used to diagnose PSC patients as Slow Progressors, Moderate Progressors and Rapid Progressors.
