<qa>  What is the average duration of follow-up?This is a multicenter, randomized, controlled trial of high dose ursodiol versus placebo for patients with primary sclerosing cholangitis PSC. The average duration of follow-up will be approximately five years with important clinical endpoints such as death, eligibility for liver transplantation, changes in histology and cholangiogram as well as liver biochemistries and quality of life data collected. 