A comparison of interventional clinical trials in rare versus non-rare diseases: an analysis of ClinicalTrials.gov
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RESEARCH
Open Access
A comparison of interventional clinical trials in rare versus non-rare diseases: an analysis of ClinicalTrials.gov Stuart A Bell and Catrin Tudur Smith*
Abstract Objectives: To provide a comprehensive characterisation of rare disease clinical trials registered in ClinicalTrials.gov, and compare against characteristics of trials in non-rare diseases. Design: Registry based study of ClinicalTrials.gov registration entries. Methods: The ClinicalTrials.gov registry comprised 133,128 studies registered to September 27, 2012. By annotating medical subject heading descriptors to condition terms we could identify rare and non-rare disease trials. A total of 24,088 Interventional trials registered after January 1, 2006, conducted in the United States, Canada and/or the European Union were categorised as rare or non-rare. Characteristics of the respective trials were extracted and summarised with comparative statistics calculated where appropriate. Main outcome measures: Characteristics of interventional trials reported in the database categorised by rare and non-rare conditions to allow comparison. Results: Of the 24,088 trials categorised 2,759 (11.5%) were classified as rare disease trials and 21,329 (88.5%) related to non-rare conditions. Despite the limitations of the database we found that rare disease trials differed to non-rare disease trials across all characteristics that we examined. Rare disease trials enrolled fewer participants (median 29 vs. 62), were more likely to be single arm (63.0% vs. 29.6%), non-randomised (64.5% vs. 36.1%) and open label (78.7% vs. 52.2%). A higher proportion of rare disease trials were terminated early (13.7% vs. 6.3%) and proportionally fewer rare disease studies were actively pursuing, or waiting to commence, enrolment (15.9% vs. 38.5%). Conclusion: Rare disease interventional trials differ from those in non-rare conditions with notable differences in enrolment, design, blinding and randomisation. However, clinical trials should aim to implement the highest trial design standards possible, regardless of whether diseases are rare or not. Keywords: Rare disease clinical trial, ClinicalTrials.gov
Background In the United States (US), a rare disease is defined as having a prevalence of fewer than 200,000 affected individuals [1]. Across the European Union (EU) the definition is that the condition affects not more than 5 in 10,000 individuals [2]. The Orpha.net database, which provides a reference portal for information on rare diseases, identifies approximately 7,000 rare diseases [3]. It is often assumed that clinical trials in rare conditions differ from those of non-rare conditions. However, * Correspondence: [email protected] Department of Biostatistics, University of Liverpool, Duncan Building, Daulby Street, Liverpool L69 3GA, UK
the extent and nature of these differences is not well understood. Kesselheim et al. provide one comparative survey exploring pivotal trials in orphan versus nonorphan drug approval [4]. These authors characterised a number of
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