Influence of Detection Method and Study Area Scale on Syphilis Cluster Identification in North Carolina

BACKGROUNDIdentifying geographical clusters of sexually transmitted infections can aid in targeting prevention and control efforts. However, detectable clusters can vary between detection methods because of different underlying assumptions. Furthermore, because disease burden is not geographically h...

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Bibliographic Details
Published in:	Sexually transmitted diseases 2016-04, Vol.43 (4), p.216-221
Main Authors:	Escamilla, Veronica, Hampton, Kristen H., Gesink, Dionne C., Serre, Marc L., Emch, Michael, Leone, Peter A., Samoff, Erika, Miller, William C.
Format:	Article
Language:	eng
Subjects:	Adult Burden Census Cluster Analysis Clusters Composition Demographic aspects Demographics Demography Detection Disease prevention Female Historical account Humans Identification Incidence Infection Infections Male North Carolina - epidemiology Original Study Population statistics Resource allocation Sexually transmitted diseases Sexually Transmitted Diseases - epidemiology Spatial discrimination Syphilis Syphilis - epidemiology Treponema pallidum Urban areas
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Summary:	BACKGROUNDIdentifying geographical clusters of sexually transmitted infections can aid in targeting prevention and control efforts. However, detectable clusters can vary between detection methods because of different underlying assumptions. Furthermore, because disease burden is not geographically homogenous, the reference population is sensitive to the study area scale, affecting cluster outcomes. We investigated the influence of cluster detection method and geographical scale on syphilis cluster detection in Mecklenburg County, North Carolina. METHODSWe analyzed primary and secondary syphilis cases reported in North Carolina (2003–2010). Primary and secondary syphilis incidence rates were estimated using census tract–level population estimates. We used 2 cluster detection methodslocal Moranʼs I using an areal adjacency matrix and Kulldorffʼs spatial scan statistic using a variable size moving circular window. We evaluated 3 study area scalesNorth Carolina, Piedmont region, and Mecklenburg County. We focused our investigation on Mecklenburg, an urban county with historically high syphilis rates. RESULTSSyphilis clusters detected using local Moranʼs I and Kulldorffʼs scan statistic overlapped but varied in size and composition. Because we reduced the scale to a high-incidence urban area, the reference syphilis rate increased, leading to the identification of smaller clusters with higher incidence. Cluster demographic characteristics differed when the study area was reduced to a high-incidence urban county. CONCLUSIONSOur results underscore the importance of selecting the correct scale for analysis to more precisely identify areas with high disease burden. A more complete understanding of high-burden cluster location can inform resource allocation for geographically targeted sexually transmitted infection interventions.
ISSN:	0148-5717 1537-4521