How much does distance limit the pool of potential clinical trial participants in the United States?
Creators: name: M C Collet
Publisher: name: F1000 Research Limited
Year: 2017

description: <i>Background</i><br><br>There are often policies at US trial sites that participants live in close proximity to the sites.  That raises the question of how distance alone reduces the pool of potential participants.<br><br><i>Objectives</i><br><br>The percentage of the US population within various radii of recruiting clinical trial sites could provide insight into the percentage of people with ALS who are automatically eliminated from today’s trials by distance.<br><br><i>Methods</i>


	On 1-May-2017, search clinicaltrials.gov for Open, Recruiting US ALS trials.
	Assemble zip codes for those sites.
	Use zip-codes.com data and Radius Finder v2.0.0.0 to find zip codes and populations within selected radii of each trial site.
	
		This Radius Finder calculates center-to-center distance.  Results for each distance were de-duplicated. If a zip code was found within multiple trial radii, the population was counted exactly once.
		Populations within zip codes were based on 2010 US Census Bureau data, as was the total US population used.
	
	
	Calculate the percent of the US population within each radius. 

<i>Results</i><br><br>Fifty-one recruiting trials involving ALS were found on 1-May-2017, at clinicaltrials.gov.  <br><br>Of those trials, 23 were marked as interventional trials.<br>     For all 51 recruiting trials (157 locations, 66 unique zip codes) --<br>          16% of the US population was within 10 miles.<br>          39% within 25 miles<br>          55% within 50 miles<br>          73% within 100 miles<br>          92% within 250 miles<br>     For the 23 recruiting interventional trials (81 locations, 46 unique zip codes)<br>          12% within 10 miles<br>          29% within 25 miles<br>          41% within 50 miles<br>          60% within 100 miles<br>          89% within 250 miles<br><br>Forty percent of Americans were more than 100 miles away from <i>any</i> recruiting interventional ALS trial.<br><br>Demographics within the 25-mile radius for interventional trials:<br>     White:  66%<br>     Male:  49%<br><br>For the 25-mile interventional trial radius, 62% of the zip codes in that radius were in proximity to only one clinical trial. <br><br>The maximum number of trials in any one zip code was 9, in 02114 (Boston).  One percent of the US population is within 25 miles of 02114.<br><br><i>Discussion</i><br><br>The percent of US population within various distances of recruiting trial sites seemed like a simple factor that could be used along with US ALS population, clustering, eligibility criteria, etc. to model the potential trial candidate pool.<br><br>A most simplistic example -- If there are 20,000 people with ALS in the US and half of them meet eligibility criteria and they are distributed as the US population, then approximately 2900 would be within 25 miles of some interventional trial.  As important, 7100 would be farther than 25 miles away from any recruiting interventional trial.<br><br><i>Conclusion</i><br><br>Distance limits both the number of potential clinical trial participants and the choices that people with ALS have to participate in clinical research.<br><br>Reducing the need to travel to trial sites could help mitigate both problems.