An analysis of blinding success in a randomised controlled trial of fish oil omega-3 fatty acids

Abstract

Introduction: Incidental reports collected in clinical trials suggest that amongst participants, omega-3 fatty acids derived from fish oil ('omega-3') may be difficult to blind.

Materials and methods: We conducted a systematic evaluation of blinding success in a 24-week trial of omega-3 versus an oil-based placebo. Within 1 week of supplement commencement (Week 1), a blinding questionnaire was completed by 131 children enrolled in a trial of omega-3 for the treatment of disruptive behaviour disorders. A version of the questionnaire was also completed by their parents at Week 1, and by the children at the end of supplement administration (Week 24).

Results: Participants were unable to differentiate omega-3 from placebo, and accuracy did not improve as a function of: the confidence of guesses, reason for guesses, notice of any change, beliefs about what should change, or time. Child and parent guesses also showed high concordance.

Conclusion: Taken together, these data provide strong evidence that the identity of omega-3 can be blinded to participants.

Trial registration: ClinicalTrials.gov NCT00819429.