A comparison of sensitivity analyses of the effect of wound duration on wound healing

The effect of an unmeasured exposure on the association between an exposure and outcome can never be fully known in an observational study. The purpose of the current study was to evaluate the sensitivity to unmeasured confounding of the previously published association between wound duration and wound healing in a chronic venous leg ulcer. This was estimated using two methods of sensitivity analysis, called Rosenbaum's method and Greenland's external adjustment. The association between wound duration and wound healing was insensitive to confounding unless the odds ratio for the association between the confounder and a younger wound was almost nine (Rosenbaum). In fact, the association between this hypothetical confounder and healing must have an odds ratio of 100 to remove the effect of duration fully (Greenland). Both of these techniques provide useful and complementary information when assessing the effects of a potential unmeasured confounder.