The effect of question order on outcomes in the orbital core outcome set for alcohol brief interventions among online help-seekers (QOBCOS): Findings from a randomised factorial trial

OBJECTIVE: A core outcome set (COS) has been developed in alcohol brief intervention (ABI) research through international consensus. This study aimed to estimate order effects among questions in the COS. METHODS: Individuals aged 18 or older who searched online for alcohol-related help were invited to complete the COS. The order of questions was randomised following a factorial design. Primary outcomes were order effects among the COS items and patterns of attrition. RESULTS: Between 21/10/2020 and 26/11/2020, we randomised 7334 participants, of which 5256 responded to at least one question and were available for analyses. Current non-drinkers were excluded. We found evidence of higher self-reported average consumption and odds of harmful and hazardous drinking was found among those who first answered questions on recent consumption and impact of alcohol use. Lower self-reported recent consumption was found among those first asked about average consumption. Quality of life (QoL) was reported lower among those who first responded to when questions on impact of alcohol use were asked first, which in turn was lower among those who first answered question on when average consumption and QoL were asked first. Attrition was lowest when average consumption was asked first, and highest when QoL or impact of alcohol use was asked first. Median completion time for the COS was 4.3 min. CONCLUSIONS: Question order affects outcomes and attrition. If the aim is to minimize attrition, consumption measures should be asked before QoL and impact of alcohol use; however, this order impacts self-reported alcohol consumption and so researchers should be guided by study priorities. At a minimum, all participants should be asked the same questions in the same order. TRIAL REGISTRATION: The trial was prospectively registered (ISRCTN17954645).