The investigators propose to pool data from several cohorts. They name 6 countries – are there 6 distinct cohorts? Roughly how many people are in these cohorts? how many of them have received Sofosbuvir and Simeprevir? How do they propose to use the RCT data obtained from the Osiris trial to inform their analysis of the observational cohorts? The investigators should clarify whether they are aiming to assess effectiveness (i.e. comparison with a comparison to an untreated group) or to assess outcomes among a treated cohort. Some of the language implies a comparative effectiveness aim but this does not seem to be the goal.