Limitations of this study included the lack of all cause mortality data, the extent of screening, screening outside of the study, screening prior to the study, the method used for calculating expected mortality and the referent rates of nonparticipants, nonparticipant survival, province specific population differences, the extent to which limitations of the database prevented correcting for age and other differences between participants, the generalizability of the substudy data of a single province British Columbia, and the potentially large impact of selection bias lasix 40 mg tablet