A workflow spatial scan statistic.

We propose a modification of the spatial scan statistic that takes account of workflow, which is the movement of individuals between home and work. The objective is to detect clusters of disease in situations where exposure occurs in the workplace, but only home address is available for analysis. In these situations, application of the usual spatial scan statistic does not account for possible differences between home and work address, thereby reducing the power of detection. We describe an extension to the usual spatial scan statistic that uses workflow data to search for disease clusters resulting from workplace exposure. We also present results from simulations that demonstrate the increased power of the workflow scan statistic over the usual scan statistic for detecting clusters arising from exposures in the workplace. Copyright 2006 John Wiley & Sons, Ltd.