Abstract
Background. Over-volunteering refers to situations where healthy human volunteers (HVs) participating to clinical trials do not respect exclusion periods between trials, usually to maximize financial gains. By doing so, HVs expose themselves to potential safety risks and may compromize the trials’ data integrity. The extent of this phenomenon is poorly documented in the scientific litterature.
Objectives. We sought to estimate the rate of over-volunteering based on trial enrollment data collected since 1995 by the Japan Association of Contract Institutes for clinical Pharmacology (JACiC) . We also sought to review key issues related to over-volunteering and to reflect about effective systems that could address this phenomenon around the world.
Methods. Our study is based on yearly data on trial enrollment between 2004 and 2023 at participating Clinical Research Units (CRUs) published on the website of the JACiC. We focus on the number of over-volunteering attempts detected by JACiC’s Subject Matching System in healthy volunteers studies as data reflecting the reality of over-volunteering in Japan. We examine the Over-Volunteering Prevention Service (TOPS) in the UK as another example of functioning registries.
Results. Out of a total of more than 860,000 HVs screened for participation in approximately 20 Phase I research units for 20 years, we found rates of over-volunteering sustained at relatively constant levels around 2 to 3% every year, including during the COVID-19 pandemic 2019 to 2021 period. This stable rate of over-volunteering attempts contrasts with the data from a single research site in the UK where the TOPS system was implemented and progressively decreasing over-volunteering rates were observed over time.
Conclusions. The JACiC data published here are the first to provide objective evidence on its frequency through over 20 years of data collection in Japan and show the significant and stable occurrence of this phenomenon. To assess between-country differences in over-volunteering rates, collection and publication of similar data from other countries, including from privately-operated registries, would be very valuable. Finally, consideration should be given to the implementation of compulsory HV registries on a national or multinational basis as the best way to prevent over-volunteering and its detrimental effects on HVs safety and on scientific data integrity.