title: A model-adjusted space-time scan statistic with an application to syndromic surveillance.
abstract: The space-time scan statistic is often used to identify incident disease clusters. We introduce a method to adjust for naturally occurring temporal trends or geographical patterns in illness. The space-time scan statistic was applied to reports of lower respiratory complaints in a large group practice. We compared its performance with unadjusted populations from: (1) the census, (2) group-practice membership counts, and on adjustments incorporating (3) day of week, month, and holidays; and (4) additionally, local history of illness. Using a nominal false detection rate of 5%, incident clusters during 1 year were identified on 26, 22, 4 and 2% of days for the four populations respectively. We show that it is important to account for naturally occurring temporal and geographic trends when using the space-time scan statistic for surveillance. The large number of days with clusters renders the census and membership approaches impractical for public health surveillance. The proposed adjustment allows practical surveillance.
authors.affiliation: Department of Ambulatory Care and Prevention, Harvard Medical School, Harvard Pilgrim Health Care, Boston, MA 02215, USA. ken_kleinman@harvardpilgrim.org
authors.forename: K P
authors.initials: KP
authors.lastname: Kleinman
authors.forename: A M
authors.initials: AM
authors.lastname: Abrams
authors.forename: M
authors.initials: M
authors.lastname: Kulldorff
authors.forename: R
authors.initials: R
authors.lastname: Platt
mesh_terms: D019352:Censuses; D003141:Communicable Diseases / Q000453:epidemiology*; D004196:Disease Outbreaks / Q000517:prevention & control*; D004812:Epidemiologic Methods; D006801:Humans; D008404:Massachusetts / Q000453:epidemiology; D015233:Models, Statistical; D011159:Population Surveillance / Q000379:methods*; D012189:Retrospective Studies; D013029:Space-Time Clustering