+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Geographic Information Systems to Assess External Validity in Randomized Trials



Geographic Information Systems to Assess External Validity in Randomized Trials



American Journal of Preventive Medicine 53(2): 252-259



To support claims that RCTs can reduce health disparities (i.e., are translational), it is imperative that methodologies exist to evaluate the tenability of external validity in RCTs when probabilistic sampling of participants is not employed. Typically, attempts at establishing post hoc external validity are limited to a few comparisons across convenience variables, which must be available in both sample and population. A Type 2 diabetes RCT was used as an example of a method that uses a geographic information system to assess external validity in the absence of a priori probabilistic community-wide diabetes risk sampling strategy. A geographic information system, 2009-2013 county death certificate records, and 2013-2014 electronic medical records were used to identify community-wide diabetes prevalence. Color-coded diabetes density maps provided visual representation of these densities. Chi-square goodness of fit statistic/analysis tested the degree to which distribution of RCT participants varied across density classes compared to what would be expected, given simple random sampling of the county population. Analyses were conducted in 2016. Diabetes prevalence areas as represented by death certificate and electronic medical records were distributed similarly. The simple random sample model was not a good fit for death certificate record (chi-square, 17.63; p=0.0001) and electronic medical record data (chi-square, 28.92; p<0.0001). Generally, RCT participants were oversampled in high-diabetes density areas. Location is a highly reliable "principal variable" associated with health disparities. It serves as a directly measurable proxy for high-risk underserved communities, thus offering an effective and practical approach for examining external validity of RCTs.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 059771774

Download citation: RISBibTeXText

PMID: 28237634

DOI: 10.1016/j.amepre.2017.01.001


Related references

The use of Geographic Information System (GIS) and non-GIS methods to assess the external validity of samples postcollection. Journal of Veterinary Diagnostic Investigation 21(5): 633-640, 2009

The case for randomized controlled trials to assess the impact of clinical information systems. Journal of the American Medical Informatics Association 18(2): 173-180, 2011

How to assess the external validity and model validity of therapeutic trials: a conceptual approach to systematic review methodology. Evidence-BasedComplementaryandAlternativeMedicine2014:694804, 2014

How to assess the external validity of therapeutic trials: a conceptual approach. International Journal of Epidemiology 39(1): 89-94, 2010

The relationship between external and internal validity of randomized controlled trials: A sample of hypertension trials from China. Contemporary Clinical Trials Communications 1: 32-38, 2015

The use of geographic information systems to map and assess ecosystem services. Biodiversity and Conservation 22(1): 1-15, 2013

External validity of randomized controlled trials in COPD. Respiratory Medicine 101(6): 1313-1320, 2007

Using geographic information systems to assess pesticide risks to groundwater. 2007

Using geographic information systems to assess conflicts between agriculture and development. Landscape and Urban Planning 16(4): 333-343, 1988

External Validity of Randomized Controlled Trials in Severe Asthma. American Journal of Respiratory and Critical Care Medicine 192(2): 259-261, 2015

Use of geographic information systems to assess the potential for riparian irrigation water use. 1987

Use of geographic information systems to assess risk of boll weevil infestations. Proceedings (2): 944-946, 1993

Validity of Geographic Information Systems (GIS) applied to protected cultivations. Acta Horticulturae (614(Vol 1)): 41-46, 2003

Randomized controlled trials: do they have external validity for patients with multiple comorbidities?. Annals of Family Medicine 4(2): 104-108, 2006

The external validity of randomized controlled trials; implications for clinical care. Diabetic Medicine 30(3): 259, 2013