Transcript 10_HealthData&GIS

Exploratory Analysis of
Disease Data
&
Introduction to UNC’s GIS
Reference Library
Prepared originally by Kristen Hampton
Updated and maintained by Ben Allshouse and others
Types of Investigations

Disease mapping
– Summation of spatial and spatio-temporal variation in
disease risk

Geographical Correlation Analysis
– Relationship between heath outcomes and environmental
risk factors

Disease clustering
– Raised incidence of disease in an area
– Non-random spatial pattern of disease relative to non-cases
Disease Mapping
(Zucker, J.R. Changing Patterns of Autochthonous Malaria Transmission in the United States: A Review of Recent Outbreaks.
Emerging Infectious Diseases. 1996;2(1):37-43.)
Geographical Correlation
Analysis
(Glass, G.E. et al. Infectious Disease Epidemiology and GIS: A Case Study of Lyme Disease. Geo Info Systems. 1992;2(10):65-69.)
Disease Clustering
GCA – Point Source Study
John Snow’s 1854 Map of Cholera and the Broad Street Pump


Hypothesis of disease
etiology
Layers
– Roads
– Pumps
– Case event data
(McLeod, K.S. Our sense of Snow: the myth of John Snow in medical geography. Social Science & Medicine. 2000;50:923-935.)
ID Application of GIS

“Continuum of diseases”
– Highly applicable to ‘environmental’ diseases, such as
malaria and other vector-borne diseases
– Limited applicability to non-communicable diseases, such
as MS, with weak or non-existent environmental
components
– In between are HIV and other STDs with moderately
strong links to the environment
(Tanser, F.C. et al. The application of geographical information systems to important public health problems in Africa. Int. J Health
Geographics. 2002;1:4.)
I-95 Syphilis Study
(Cook et al. What’s driving an epidemic? The Spread of Syphilis Along an Interstate Highway in Rural North Carolina. Am. J of
Public Health. 1999 Mar;89(3):369-373.)
I-95 Syphilis Study
(Cook et al. What’s driving an epidemic? The Spread of Syphilis Along an Interstate Highway in Rural North Carolina. Am. J of
Public Health. 1999 Mar;89(3):369-373.)
Issues

Confounding

Resolution / Aggregation level
– Patient confidentiality
– Spatial accuracy
– Ecological Fallacy (individual v. group)

Temporal relationship between exposure and
disease
Exploratory Analysis of
HIV in North Carolina

Screening and Tracing for Acute HIV Transmission
(STAT)
– Collaboration between UNC-CH CFAR and NC DHHS
– Developed a system using HIV biomarkers to determine the time
of transmission (incident cases)
– All HIV test samples sent to state labs are staged with the STAT
protocol

Records are mapped according to self-reported zip
code of residence
– Sample data for 1 year:
110,000 mappable records
500 prevalent cases
100 incident cases
Goal

Given a table of patient records with disease X in
North Carolina, create choropleth maps of
i.
case count,
ii.
density of cases per square mile, and
iii. population density (persons per square mile)
by zip code, shown with major highways.
Patient ID Street Address
1
----2
-----
Road Classification
Major Highway
No. of Cases
0
1
2
3
4-9
City
---------
State
NC
NC
Zip
---------
Gender
1
1
Information Needed

Tabular Disease Data (Given*)
– *.dbf (dbase) or *.txt (text) file formats

GIS Data
– Polygon shapefile of NC zip codes
– Line shapefile of NC roads

Attribute Data
– Zip code area and population
* All disease data introduced in this exercise is fictional and for
demonstration purposes only.
Resources



http://www.lib.unc.edu/reference/gis/
Amanda Henley
GIS Reference Librarian, Davis Library
[email protected]
ArcGIS desktop Help
Data Confidentiality

Health data is confidential
– Issue of privacy for health data
– As a researcher you must seek training about, and
proactively protect data confidentiality

Environmental data is confidential as well
– Privacy issue also applies to any environmental data that
can be associated with an individual

How will you protect data confidentiality in this
course?
– Identify data that might be confidential (address, etc.)
– Take action to protect it (do not send it to others, do not
discuss it or use it in a way that would allow others to
identify/target individuals, erase the data after you use it,
always ask yourself what else you can do)
Exercise

Handout
– Searching UNC’s GIS Database

Additional Exercises
– Adding X,Y Coordinates of Polygon Centroids
– Creating Raster Density Maps from Point Layers
– Geocoding a Table of Addresses