Background The European Huntington's Disease Network's (EHDN) REGISTRY is an observational, prospective, longitudinal, multi-national, multi-centre cohort study of Huntington's disease (HD). It is the largest study of HD to date, and collects valuable phenotypical data and biospecimens on individuals who are at risk of, premanifest or manifest for HD, and includes age and gender-matched control participants.

Aims REGISTRY aims to establish a well-characterised European-based HD population to expedite high-quality research to improve our knowledge of this disease and to work towards discovering and developing therapies to delay or slow HD.

Methods/techniques REGISTRY follows a prospective study design, with participants attending annual visits. Pseudonymised clinical data are stored centrally on a customised webportal (http://www.euro-hd.net/registry). Biospecimens are processed and stored centrally at BioRep, Milan, Italy. All data are captured online and are subject to regular quality control checks for plausibility and accuracy.

Results/outcome REGISTRY data have been collected from 16 European countries. Over 6500 participants have contributed phenotypical data, and of those, more than 4000 participants have contributed biosamples for further use in large-scale genetic modifier and biomarker HD studies. On average, 100 participants are enrolled into REGISTRY each month, and approximately 200 biospecimens (including resubmissions from existing participants) are submitted. A summary of the key study metrics including demographics and disease stage of the REGISTRY cohort are presented.

Conclusions REGISTRY has been successful in establishing a well-characterised European-based HD cohort. The study has expedited the coordination and implementation of clinical trials of promising compounds. The study protocol was amended in 2009 to include retrospective data collection (pre-enrolment to REGISTRY), video-recording, and the development and validation of novel/additional endpoints for therapeutic interventions. The milestones accomplished to implement the revised protocol will be summarised together with an overview of future directions.