Background: Outcome reporting in bariatric surgery needs uniformity. A core outcome set is an agreed minimum set of outcomes reported in all studies of a particular condition, but members of the bariatric multidisciplinary team might value outcomes differently. The aim of this study was to summarise existing outcome reporting in bariatric surgery, to inform the development of a core outcome set, and to compare outcomes selected as important by type of health professional.
Methods: Outcomes reported in randomised controlled trials (RCTs) and large non-randomised studies, identified by a systematic review, were listed verbatim. Frequency of outcome reporting and uniformity of definition were assessed. A questionnaire to rate the importance of each outcome was completed by members of the bariatric multidisciplinary team. Responses to each item were scored as 1 (not essential) to 9 (absolutely essential). We ranked outcomes according to percentage deemed important (7-9) and according to respondents by type of health professional.
Findings: We identified 1088 individual outcomes from 90 studies (39 RCTs), grouped them into health domains, and presented them as a questionnaire with 131 items to 489 multidisciplinary team members. Most outcomes (n=920, 85%) were reported only once. The largest outcome domain was surgical complications, and 432 outcomes (42%) corresponded to an adverse event. Only a quarter of outcomes (n=461) were defined, and were often contradictory. For questionnaire responders (n=164, response rate 33·5%), most were surgeons (n=80, 48·8%), followed by dietitians (n=31, 18·9%), nurses (n=24, 14·6%), physicians (n=12, 7·3%), and others (n=16, 9·9%). Improvement in diabetes was the top outcome for all health professionals. Seven of the surgeon's top ten outcomes were adverse events, compared with three for other health professionals. Groups valued a measure of weight differently (third vs 15th for other health professionals and surgeons, respectively).
Interpretation: This study shows that the assessment of bariatric surgery focuses largely on adverse events and resolution of comorbidity, but that reporting is inconsistent and ill-defined. Substantial variation between the views of surgeons and those of other health professionals was evident. The next step is to provide feedback to participants and to survey their views again before a final consensus meeting to produce a core outcome set for the Benefits and Adverse events in BARIAtric surgery Clinical Trials (BARIACT) as a solution to this problem.
Funding: National Institute for Health Research (NIHR), and the NIHR Health Technology Assessment programme. This work was also undertaken with the support of the MRC ConDuCT-II Hub (Collaboration and innovation for Difficult and Complex randomised controlled Trials In Invasive procedures, MR/K025643/1).
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