Adaptations for finding irregularly shaped disease clusters

<p>Abstract</p> <p>Background</p> <p>Recent adaptations of the spatial scan approach to detecting disease clusters have addressed the problem of finding clusters that occur in non-compact and non-circular shapes – such as along roads or river networks. Some of these approaches may have difficulty defining cluster boundaries precisely, and tend to over-fit data with very irregular (and implausible) clusters shapes.</p> <p>Results & Discussion</p> <p>We describe two simple adaptations to these approaches that can be used to improve the effectiveness of irregular disease cluster detection. The first adaptation penalizes very irregular cluster shapes based on a measure of connectivity (non-connectivity penalty). The second adaptation prevents searches from combining smaller clusters into large super-clusters (depth limit). We conduct experiments with simulated data in order to observe the performance of these adaptations on a number of synthetic cluster shapes.</p> <p>Conclusion</p> <p>Our results suggest that the combination of these two adaptations may increase the ability of a cluster detection method to find irregular shapes without affecting its ability to find more regular (i.e., compact) shapes. The depth limit in particular is effective when it is deemed important to distinguish nearby clusters from each other. We suggest that these adaptations of adjacency-constrained spatial scans are particularly well suited to chronic disease and injury surveillance.</p

Examining the relationship between active travel, weather, and the built environment: A multilevel approach using a GPS-enhanced dataset

This study examines how the built environment and weather conditions influence the use of walking as a mode of transport. The Halifax Regional Municipality in Nova Scotia, Canada is the study area for this work. Data are derived from three sources: a socio-demographic questionnaire and a GPS-enhanced prompted recall time-use diary collected between April 2007 and May 2008 as part of the Halifax Space-Time Activity Research project, a daily meteorological summary from Environment Canada, and a comprehensive GIS dataset from the regional municipality. Two binary logit multilevel models are estimated to examine how the propensity to use walking is influenced by the built environment and weather while controlling for socio-demographic characteristics. The built environment is measured via five attributes in one model and a walkability index (derived from the five attributes) in the other. Weather conditions are shown to affect walking use in both models. Although the walkability index is significant, the results demonstrate that this significance is driven by specific attributes of the built environment—in the case of this study, population density and to a lesser extent, pedestrian infrastructure

An integrated framework for the geographic surveillance of chronic disease

<p>Abstract</p> <p>Background</p> <p>Geographic public health surveillance is concerned with describing and disseminating geographic information about disease and other measures of health to policy makers and the public. While methodological developments in the geographical analysis of disease are numerous, few have been integrated into a framework that also considers the effects of case ascertainment bias on the effectiveness of chronic disease surveillance.</p> <p>Results</p> <p>We present a framework for the geographic surveillance of chronic disease that integrates methodological developments in the spatial statistical analysis and case ascertainment. The framework uses an hierarchical approach to organize and model health information derived from an administrative health data system, and importantly, supports the detection and analysis of case ascertainment bias in geographic data. We test the framework on asthmatic data from Alberta, Canada. We observe high prevalence in south-western Alberta, particularly among Aboriginal females. We also observe that persons likely mistaken for asthmatics tend to be distributed in a pattern similar to asthmatics, suggesting that there may be an underlying social vulnerability to a variety of respiratory illnesses, or the presence of a diagnostic practice style effect. Finally, we note that clustering of asthmatics tends to occur at small geographic scales, while clustering of persons mistaken for asthmatics tends to occur at larger geographic scales.</p> <p>Conclusion</p> <p>Routine and ongoing geographic surveillance of chronic diseases is critical to developing an understanding of underlying epidemiology, and is critical to informing policy makers and the public about the health of the population.</p

Geographic hierarchies of diagnostic practice style in cerebrovascular disease

Diagnostic practice style describes the ways in which physicians diagnose information about disease. Like practice style effects in general, diagnostic practice style effects may emerge as the result of training, inter-personal relationships between professionals, medical enthusiasm for particular diagnoses and patient-physician interactions. In this study we analyze the ways in which patterns of diagnostic practice style associated with cerebrovascular disease varies at different socio-geographical scales in the province of Alberta, Canada. We use hierarchical linear models to partition a measure of diagnostic practice style into four levels of observation: the physician level, the facility level, the municipality level and the regional (census division) level. We model a variety of fixed effects related to physician attributes, their practice, the facilities they work in and the municipalities within which their facilities operate. Our results suggest that attributes related to physicians and the facilities and municipalities in which they work all contribute to patterns of diagnostic practice style. Physicians working in rural and urban municipalities have different practice style patterns even after controlling for the types of facilities they work in, their professional medical specialization and their workload. Similar to other research, our results reveal that physicians have different diagnostic practice styles with members of the same sex than members of the opposite sex. Geographic variations in diagnostic practice style may obscure changes in the epidemiology of cerebrovascular disease in rural communities, and provide indirect evidence that the quality and/or timeliness of diagnosis may be worse in rural Alberta.Canada Cerebrovascular disease Diagnosis Physicians Diagnostic practice styles Geographic variation

Sensitivity and positive predicted value for cluster pattern 1 ('two clusters')

<p><b>Copyright information:</b></p><p>Taken from "Adaptations for finding irregularly shaped disease clusters"</p><p>http://www.ij-healthgeographics.com/content/6/1/28</p><p>International Journal of Health Geographics 2007;6():28-28.</p><p>Published online 5 Jul 2007</p><p>PMCID:PMC1939838.</p><p></p

Sensitivity and positive predicted value for cluster pattern 3 ('Ring')

<p><b>Copyright information:</b></p><p>Taken from "Adaptations for finding irregularly shaped disease clusters"</p><p>http://www.ij-healthgeographics.com/content/6/1/28</p><p>International Journal of Health Geographics 2007;6():28-28.</p><p>Published online 5 Jul 2007</p><p>PMCID:PMC1939838.</p><p></p