Table 2.

Advantages and disadvantages of sources of unpublished data described by interview respondents

Sources of unpublished data	Advantages	Disadvantages
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• More or different data may appear in financial publications compared to the scientific literature	• Can suggest that unpublished data exist, but the data must still be obtained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