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Significant number of clinical trials go unreported

A significant number of large clinical trials go unreported, which could “threaten the credibility” of published evidence, according to a research report published in the Annals of Internal Medicine.

“Loss of information is the most worrisome when the largest and thus potentially most informative trials both remain unpublished and lack posted results after completion,” Athina Tatsioni, MD, of the University of Ioannina School of Health Sciences, Greece, and colleagues wrote.

Researchers used ClinicalTrials.gov to search for studies with a start date after June 1, 2007, and a completion date before June 1, 2012, and later identified the 500 trials with the largest participant enrollment that were unpublished and had no results posted as of April 22, 2016. Trials that were nonrandomized, cluster-randomized, and non-preregistered were excluded. Researchers conducted a separate search to determine if any of the trials were published or had results reported between April 2016 and January 2019.

They identified 146 large randomized controlled trials with no results published or posted on ClinicalTrials.gov. After reaching out to contact persons and investigators from the trials and completing an additional search on clinicalstudydatarequest.com, researchers narrowed their results to 70 long-unreported and unpublished trials, only three of which had results available on ClinicalTrials.gov as of January 2019.

Among the remaining 67 long-unreported trials, there were 87,883 participants involved. The trials had a median enrollment of 765 participants and went unreported for a median of 9 years after completion. Enrolled participants were adults in 58 trials, mixed ages in 11 trials and children in one trial.

Major disease categories evaluated in the trials included cardiovascular disease (n = 13), infection (n = 12), psychiatric diseases (n = 9), women’s health and obstetrics (n = 6) allergy (n = 5) and neurological disease (n = 5). Among the trials published from 2016 to 2019, all but one had been completed in 2011 to 2012.

Large clinical trials left unreported for nearly 4 years or more after completion were unlikely to be published later or have results posted on ClinicalTrials.gov. Researchers noted that large, unreported trials could represent a substantial amount of evidence in fields with several treatments available.

“The conduct of research in humans comes with inviolable responsibilities, including the commitment to share what has been learned,” Joshua D. Wallach, MS, PhD, and Harlan M. Krumholz, MD, SM, of the Yale School of Public Health and Yale School of Medicine, wrote in an editorial accompanying the study. “When trial results are not made publicly available for years after study completion, patients, institutional review boards, clinicians, researchers, and the public must rely on incomplete evidence, which may lead to misconceptions about the efficacy and safety of interventions. The time has arrived to address this threat to trust and science.” – by Erin Michael

Disclosures: Healio Primary Care Today was unable to confirm relevant financial disclosures prior to publication.