Two-Stage Recruitment Design to Reduce Magnetic Resonance Imaging Screening Cost for a Theoretical Clinical Trial of White Matter Hyperintensity Progression.

Background: White matter hyperintensities (WMH) and their progression are associated with risk of dementia and stroke, so are an important target for clinical trials. The cost of broad magnetic resonance imaging (MRI) screening to identify eligible individuals, however, limits the feasibility of designing clinical trials targeting WMH. A low-cost retinal or clinical screening measure before MRI could reduce recruitment costs versus an MRI-only screening design in a hypothetical clinical trial.

Methods and results: Data from the Atherosclerosis Risk in Communities study with valid retinal and WMH measurements (N=1311) were used. To identify a population at greater likelihood of significant WMH on MRI and thus reduce the number of screening MRIs required, we evaluated 3 theoretical prescreening measures: (1) retinal, (2) clinical, (3) combined clinical-retinal. Given a target sample for clinical trials (N=646), we calculated screening sample sizes based on the proportion within the population having an elevated score for each prescreening measure (separately) multiplied by the proportion of significant WMH among those with that prescreening feature. Recruitment costs were calculated using estimated retinal and MRI cost estimates. Compared with the estimated cost of MRI-only screening (>$4.24 million, requiring MRI on 6526 participants), prescreening for a high clinical score resulted in total cost of $2.47 million, with an initial screening group of 52 778 participants, with MRI in 3801. A high clinical-retinal score cutoff resulted in costs of $2.9 million while requiring 13 572 participants, with 3801 completing MRI.

Conclusions: A 2-stage design with low-cost prescreening measures is a promising approach, resulting in reduced theoretical recruitment costs compared with an MRI-only design.