An Analysis of Blinding Success in a Randomised Controlled Trial of Fish Oil Omega-3 Fatty Acids

Abstract

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