Abstract A52: Use of geographic information systems to identify geographic clustering of screening colonoscopy resources with the city of Chicago
Authors: Naylor Keith B. , Kim Karen E. 
Published: October 2015

Background: In Illinois for the year 2014, colorectal cancer (CRC) is projected to cause 2,190 deaths, making it the leading cause of non-tobacco related cancer mortality. African American Illinois residents have an approximately 7% greater incidence and a 30% higher mortality rate when compared to white residents. Guideline consistent routine screening is known to reduce death due to CRC. However, according to the Centers for Disease Control, Illinois currently ranks in the lowest quartile amongst states for up-to-date screening of adults age 50 to 75 years.

Chicago's South Side includes 34 of the city's 77 recognized community areas and is home to a combined population of more than 800,000 residents, of whom greater than 75% are African American. The contiguous communities that make up the South Side cover approximately 60% of Chicago's land area. Relatively homogenous minority communities, such as Chicago's South Side, are prone to the development of healthcare inequities that may result in the development of healthcare disparities.

Objective: The objectives of this study are to use geographic information systems (GIS) and spatial analysis techniques to investigate geographic variations in the distribution of colonoscopy sites within the City of Chicago.

Methods: CRC incidence data (1986-2010) by Zip code was obtained from the Illinois State Cancer Registry. Population characteristics by ZIP code (sex, median age, total population, median household income, racial/ethnic makeup) were obtained from the 2010 Census and Demographic Profile. The locations of colonoscopy sites were identified through a combination of internet search; review of Gastroenterology organization membership rosters; and expert opinion. Colonoscopy site addresses were geocoded using GPS Visualizer. Mapping and testing for spatial autocorrelation (global and local) were performed using STATA 13.

Results: 55 colonoscopy sites were identified within the City of Chicago. 15 of 55 (27%) colonoscopy sites were located within Chicago's South Side. The geocoded address of each colonoscopy site was mapped to assess resource distribution. Testing for local spatial autocorrelation of colonoscopy sites by ZIP code identified significant local autocorrelation centered at Zip code 60613 (Moran's Ii = 131.399, p = 0.046), located within Chicago's North Side. Testing for global autocorrelation using population characteristics and CRC incidence data by ZIP code revealed evidence of significant global autocorrelation for areas with increased median household income (Moran's I = 0.532, p &lt; 0.001).

Conclusions: There is unequal distribution of colonoscopy sites across the City of Chicago with 15 sites (27%) located on Chicago's South Side. Testing for local spatial autocorrelation was significant for clustering of colonoscopy sites near the Zip code 60613, located on Chicago's North Side. Significant global autocorrelation was found related to increasing median household income. The clustering of colonoscopy sites near ZIP codes with increased median household incomes represents a healthcare resource inequity that may lead to persistence of disparities in CRC screening among low-income, medically underserved, and/or minority communities.

Citation Format: Keith B. Naylor, Karen E. Kim. Use of geographic information systems to identify geographic clustering of screening colonoscopy resources with the city of Chicago. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr A52.