In nine of 17 outcome comparisons, there were no significant differences between results of randomized controlled trials and database studies analysed using standard biostatistical methods or PERR analysis. In eight comparisons, Cox adjusted hazard ratios in the database differed significantly from the results of the randomized controlled trials, suggesting unmeasured confounding. In seven of these eight, PERR adjusted hazard ratios differed significantly from Cox adjusted hazard ratios, whereas in five they didn’t differ significantly, and in three were more similar to the hazard ratio from the randomized controlled trial, yielding PERR results more similar to the randomized controlled trial than Cox (P