Professor Peter Gøtzsche, director of the Nordic Cochrane Centre, said: "We wished to compare the information in the protocols with the information provided to the patients in order to evaluate whether the trials were ethical and necessary and whether essential information about the benefits and the harms of the drugs had been hidden from the patients."
It is difficult to get access to drug trial protocols so Professor Gøtzsche and his colleagues used the Danish Freedom of Information Act to request access to 78 trial protocols approved by a research ethics committee from October 2012 to March 2013. Eight protocols were excluded because they did not meet the research inclusion criteria. Only 17 of 34 protocols for commercially sponsored trials were unredacted, compared to 34 of 36 non-commercially sponsored trials.
The redactions were most widespread in those sections of the protocol where there is empirical evidence of substantial problems with the trustworthiness of published drug trials. These include the definition of patient outcomes, the detection and analysis of adverse events and the sponsor's access to incoming data while the study is running.
Professor Gøtzsche said: "The amount of redactions in the protocols we received was so vast that it made them rather useless for assessing the ethical justification for the studies and to identify discrepancies with subsequent publications.
"We could not identify any legitimate rationale for the redactions. The current mistrust in industry-sponsored drug trials can only change if the industry offers unconditional access to its trial protocols and other relevant documents and data."
Mikkel Marquardsen, Michelle Ogden, Peter C. Gøtzsche.
Redactions in protocols for drug trials: what industry sponsors concealed.
Journal of the Royal Society of Medicine. doi: 10.1177/0141076817750554