Use of sensitivity analysis to assess the effects on anti-hepatitis A virus antibodies of access to household water supply.

The objective of this study was to assess the impact of a possible unmeasured confounding variable in a previously published association between the effects of household water supply and positive results for hepatitis A serology. This was estimated using a path of integration between two methods of sensitivity analysis, called Rosenbaum's method and Greenland's external adjustment. The association between household water supply and positive results for hepatitis A (outcome) serology was insensitive to confounding unless the odds ratio for the association between the confounder and the outcome was > or = 4. The integration of the two sensitivity analysis methods presented proved useful when assessing the effects of a potential unmeasured confounder.