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Comment & Response
July 13, 2020

Changed Primary Outcome Between Trial Registration and Publication

Author Affiliations
  • 1Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, California
  • 2Department of Psychiatry, Veterans Affairs Palo Alto Health Care System, Palo Alto, California
JAMA Intern Med. Published online July 13, 2020. doi:10.1001/jamainternmed.2020.2183

To the Editor We read with interest the work of Anton and colleagues1 evaluating gabapentin in the treatment of alcohol use disorder. We are concerned that the authors report a positive primary outcome even though the original preregistered primary outcome was nonsignificant, suggesting that gabapentin is not effective in the way the authors assert.

The authors report a statistically significant decrease in percentage of participants with no heavy drinking days. They define this by 2 criteria: (1) self-report of no heavy drinking days and (2) no reading on the percentage of disialo carbohydrate-deficient transferrin (%dCDT) greater than 1.7% at any point in the trial. However, in both the original preregistered outcome and the supplementary protocol, a %dCDT threshold is not part of the primary outcome definition. There was no significant difference between gabapentin and placebo using the self-report criterion. Only when the %dCDT threshold was applied did the difference between the groups become statistically significant.

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