Table 2 Advantages and disadvantages of sources of unpublished data described by interview respondents

Study authors

They have the data

• Not always responsive

• Want to keep the data to themselves for their own publications

Drug companies

• Have complete clinical study reports

• Rarely responsive

• Want to know what you want to do with the data

Regulatory agencies

• Includes summary data from clinical trials

• Not a user friendly interface

• People do not know what information/data are available on the agencies websites

• Not as much information about older drugs

• Data on phase 4 studies often missing

Grey literature

Provide information about studies that may be published, for example, presented at conferences.

• Does not provide key pieces of outcome data

• Rarely peer reviewed

Law firms - class action suits in the US

• Can uncover all of the data for a given drug

• Happens for few drugs

• Tens of thousands of pages of documents to search

• Judges must agree to release the data

Grant organizations

• Provide a list of all studies they sponsor

• Sponsor a small number of studies

Marketing materials from companies and financial reviews

• More or different data may appear in financial publications compared to the scientific literature

• Can suggest that unpublished data exist, but the data must still be obtained

The media – journalists, press officers

• Companies will respond to media pressure

• Data may not be complete

Clinical trial registries

• Provide awareness of all of the trials being conducted on a certain drug in a certain area

• Results data are generally not available

• Some registries do not contain registration of Phase 1 or 4 trials