Current Issues in Randomized Clinical Trials of Neurodegenerative Disorders at Enrolment and Reporting: Diagnosis, Recruitment, Representativeness of Patients, Ethnicity, and Quality of Reporting.

Abstract

The investigator is faced with several challenges when planning a randomized clinical trial (RCT). In the early phase, issues are particularly challenging for RCTs in neurodegenerative disorders (NDD). At the time of inclusion in the study, an early and accurate diagnosis is mandatory. Variability of diagnostic criteria, mostly based on clinical grounds, lag time between onset and enrolment, and phenotypic heterogeneity are the main drivers of diagnostic complexity. High-quality data in terms of diagnostic reliability, phenotypic description, follow-up, and evaluation of outcomes are key determinants and are highly conditioned by the expertise of the investigators and center recruitment rate. Representativeness of NDD patients is mandatory to postulate the generalizability of the results of RCTs. There is, however, a systematic selection bias in terms of age (more likely to be younger), sex (more likely to be male), ethnicity (more likely to be of European/Caucasian origin), and other prognostic factors (more likely to be favorable). In the publication phase, researchers need to report properly all of the main features of the RCT. Consolidated Standards of Reporting Trials (CONSORT) facilitates the report and interpretation of RCTs, but adherence to these guidelines needs to be improved. Several issues discussed in this review may alter the internal and external validity of an RCT. To date, the impact on phenotype at study entry has often been overlooked. A differential effect of the selection of subjects and of specific clinical and nonclinical features needs to be systematically explored in the RCT planning phase.