The Trials Tracker does not measure the extent of unpublished trials. It uses an automated algorithm to search for trial publications, which is not backed up by manual searching. So in fact what it measures is the extent to which the publication of trials are indexed such that the link between the clinicaltrials.gov record and the publication can be discovered automatically.
A great many clinical trials are published, but imperfectly indexed, so are not picked up by the Trials Tracker algorithm.
I was curious to see how imperfect indexing and failure to disclose studies matched, so I downloaded the Trials Tracker raw data and looked up the first 10 "undisclosed" trials sponsored by Sanofi, as this was the sponsor with the largest number of "undisclosed" trials according to the Trials Tracker website. Those trials had the trial identifiers NCT00069888, NCT00081796, NCT00087802, NCT00087958, NCT00094081, NCT00094965, NCT00103649, NCT00104013, NCT00115570, and NCT00123565.
All except 2 of those trials had their results disclosed on Sanofi's own website (http://en.sanofi.com/Innovation/clinical_trials/our_commitments/clinical...). Of the remaining 2, one (NCT00094081) was published in a peer-reviewed journal (http://ascopubs.org/doi/full/10.1200/jco.2009.27.4449), and only one (NCT00123565) remained undisclosed after a 5 minute search of Google and Pubmed. Trial NCT00123565 was of a drug which was abandoned in clinical development in 2008, so no patient is deprived of information on a drug they are taking by the failure to disclose that study.
I do not know whether those 10 trials I happened to pick are representative. However, if they are, it suggests that the mismatch between undisclosed trials and improperly indexed trials is substantial, and that using one figure as a proxy for the other may over-estimate the extent of non-disclosure by a factor of 10.
Competing interests:
I have previously written articles (such as http://www.statsguy.co.uk/zombie-statistics-on-half-of-all-clinical-trials-unpublished/) criticising the All Trials campaign for exaggerating the extent of unpublished trials.
Rapid Response:
Re: Sixty seconds on . . . TrialsTracker
This article is very misleading.
The Trials Tracker does not measure the extent of unpublished trials. It uses an automated algorithm to search for trial publications, which is not backed up by manual searching. So in fact what it measures is the extent to which the publication of trials are indexed such that the link between the clinicaltrials.gov record and the publication can be discovered automatically.
A great many clinical trials are published, but imperfectly indexed, so are not picked up by the Trials Tracker algorithm.
I was curious to see how imperfect indexing and failure to disclose studies matched, so I downloaded the Trials Tracker raw data and looked up the first 10 "undisclosed" trials sponsored by Sanofi, as this was the sponsor with the largest number of "undisclosed" trials according to the Trials Tracker website. Those trials had the trial identifiers NCT00069888, NCT00081796, NCT00087802, NCT00087958, NCT00094081, NCT00094965, NCT00103649, NCT00104013, NCT00115570, and NCT00123565.
All except 2 of those trials had their results disclosed on Sanofi's own website (http://en.sanofi.com/Innovation/clinical_trials/our_commitments/clinical...). Of the remaining 2, one (NCT00094081) was published in a peer-reviewed journal (http://ascopubs.org/doi/full/10.1200/jco.2009.27.4449), and only one (NCT00123565) remained undisclosed after a 5 minute search of Google and Pubmed. Trial NCT00123565 was of a drug which was abandoned in clinical development in 2008, so no patient is deprived of information on a drug they are taking by the failure to disclose that study.
I do not know whether those 10 trials I happened to pick are representative. However, if they are, it suggests that the mismatch between undisclosed trials and improperly indexed trials is substantial, and that using one figure as a proxy for the other may over-estimate the extent of non-disclosure by a factor of 10.
Competing interests: I have previously written articles (such as http://www.statsguy.co.uk/zombie-statistics-on-half-of-all-clinical-trials-unpublished/) criticising the All Trials campaign for exaggerating the extent of unpublished trials.