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Comment & Response
December 2018

Protocol Deviations, Reanalyses, and Corrections to Derivative Studies of the PREDIMED Trial

Author Affiliations
  • 1Department of Preventive Medicine and Public Health, Facultad de Medicina, Clínica Universidad de Navarra, Pamplona, Spain
JAMA Intern Med. 2018;178(12):1730-1731. doi:10.1001/jamainternmed.2018.6456

To the Editor As reported elsewhere,1 my coinvestigators and coauthors of the PREDIMED trial have identified protocol deviations, including enrollment of household members without randomization, assignment to a study group without randomization of some participants at 1 of 11 study sites, and apparent inconsistent use of randomization tables at another site. Briefly, there were 425 participants who were allocated to the same group as their family member already randomized in the trial and with whom they shared the same household. In addition, 467 participants from 1 of the 11 recruiting sites were not individually randomized but rather were assigned to an intervention group based on clinics (ie, all participants attending a particular clinic, the site where the intervention was delivered for small groups of participants, received the same intervention). The original PREDIMED trial compared cardiovascular outcomes among 3 diet groups: (1) a traditional Mediterranean diet plus virgin olive oil, (2) a traditional Mediterranean diet plus nuts, and (3) a low-fat control diet. Derivative studies assessed other outcomes, including cognitive decline, breast cancer, metabolic syndrome, and lipoprotein oxidation.

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