Missing data in clinical trials is a major problem. One would expect the situation to be better for trials funded by large non-profit organisations that are free of commercial bias, and with policies for transparency and data sharing. However, in our experience with a non-profit trial funder we found this was not the case. Indeed, it was so bureaucratic that, despite the good intentions of the authors and others involved, accessing the data proved to be very difficult. We wanted to study how treatment effects in randomised clinical trials were affected by a failure to blind the outcome assessors. We therefore systematically reviewed trials where the same outcome had been assessed by both a blind and a non-blind assessor within the same trial.1 2 One eligible study was a large, well performed trial of the effect of electrical deep brain stimulation for patients with advanced Parkinson disease, published in JAMA in January 2009.3 The trial was partially funded by the Cooperative Studies Program of the Department of Veterans Affairs’ Office of Research and Development. JAMA reported UPDRS motor scores (Unified Parkinson’s Disease Rating Scale III) evaluated by blind assessors, but did not …
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A. Hrobjartsson (2013) studied this question.
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