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Clinical trials registered prospectively are less likely to veer from protocols, study finds

BMJ 2017; 358 doi: https://doi.org/10.1136/bmj.j4232 (Published 11 September 2017) Cite this as: BMJ 2017;358:j4232
  1. Susan Mayor
  1. London

Clinical trials that are registered prospectively on trial registries are more likely to be published without changes to the primary outcome or the study protocol than those not registered, a Finnish study has reported.1

“Journal editors, regulators, research ethics committees, funders, and sponsors should implement policies mandating prospective registration for all clinical trials,” said the study authors, led by An-Wen Chan, from the University of Toronto, Canada. They added, “Only with accessible, complete information can interventions be adequately evaluated for patient care.”

The researchers reviewed trial registration and resulting publications for all 113 clinical trials initiated in the region of Helsinki and Uusimaa in Finland during 2007.

Results, published in JAMA, showed that discrepancies between the original clinical trial protocol and the subsequent publication were much more common in unregistered trials (six out of 11 trials; 55%) than those prospectively listed on trial registries (three out of 47; 6%; P<0.001).

Discrepancies included changing the primary outcome from that specified in the protocol or omitting or downgrading the primary outcome defined in the registry or publication.

“The original protocol and amendments should be made publicly available so that editors, peer reviewers, and readers can identify any unacknowledged changes to protocol defined outcomes in the registry or publication,” said the study authors.

They suggested that protocols should give complete descriptions of the primary outcomes and other key elements of study plans, adding, “Amendments should be transparently reported.”

Fewer than two thirds of the trials in the study (69 trials; 61%) were prospectively registered with clinical trial registries. Those involving drugs or biologic interventions, and those with larger sample sizes were much more likely to be registered than other types of study (85% v 13%). And industry sponsored trials were more likely to be prospectively listed on trial registries than non-industry studies (87% v 38%).

Tracking the trials through to publication showed that prospectively registered trials were nearly twice as likely to be published than unregistered trials (68% v 39%; adjusted odds ratio 4.53; 95% confidence interval 1.12 to 18.34).

References

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