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Numerator-Denominator Aggregation Rules Used to Present Sub-County Environmental Health Data to the Public: Is It Possible to Maintain Confidentiality and Preserve Spatial Data Trends?

Monday, June 15, 2015: 1:00 PM
Beacon F, Sheraton Hotel
John T. Braggio , Maryland Department of Health and Mental Hygiene, Baltimore, MD
Ann Y. Liu , Maryland Department of Health and Mental Hygiene, Baltimore, MD
Jennifer Stanley , Maryland Department of Health and Mental Hygiene, Baltimore, MD
Debola Akinyemi , Maryland Department of Health and Mental Hygiene, Baltimore, MD
Clifford S. Mitchell , Maryland Department of Health and Mental Hygiene, Baltimore, MD

Key Objectives:

 

  1. Review nationally available sub-county environmental health data displays and Maryland health code/data steward sub-county data suppression rules.
  2. Present aggregated Maryland ZIP code or census tract-level statistical results using the New York State Geographic Aggregation Tool (GAT), based on four separate possible rules for cell suppression. 
  3. With input from round table participants the presenters will discuss the advantages and drawbacks of using various possible numerator/denominator aggregation rules to present sub-county environmental health data to the public.

Brief Summary:

While there are well defined data suppression rules that protect the confidentiality of state- and county-aggregated environmental health data currently available to the public, similar suppression rules have not been uniformly adopted for public accessible sub-county aggregated data.  This poses a challenge for data visualization and presentation systems such as the Maryland Tracking Network (MTN) public portal.  We tested four different rules for cell suppression as part of an effort to develop uniform rules for the MTN public portal.  The four rules evaluated were: (1) at least 12 environmental health events in the numerator and total population values (or total children tested for lead exposure) in the denominator of 1,000; (2) a numerator of 12 and denominator of 10,000; (3) a numerator of 12 and denominator of 20,000; and (4) the Medicaid “Safe Harbor” rule with a numerator of 11 and denominator of 20,000.  The health outcomes tested included 2010-2012 Maryland children’s blood lead levels of 5+ µg/dL, and 2011 Maryland hospital discharges for asthma or acute Myocardial Infarctions (MI), suicides and injuries.  The GAT was used to combine neighboring residential ZIP codes (asthma, acute MI, injuries) or census tracts (children’s blood lead test results, suicides).  Results for the four aggregation rules were compared with the un-aggregated ZIP code or census tract geographic polygons (reference, what is available to data analysts) for each of the five environmental health outcomes.  Maps were used to evaluate the preservation of spatial data trends in the reference and the four rule-based environmental health spatial displays.  Descriptive statistical measures were used to quantify the  outcomes for the four polygon aggregation rules. The utility of each of the aggregation rules as a basis for presenting sub-county aggregated environmental health data to the public will be described, and with input from roundtable participants, the presenters will discuss the merits and challenges of various aggregation rules.

Handouts
  • CSTE 2015 Roundtable Presentation.pdf (1.2 MB)
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