British researchers have published a “core outcome set” (COS) comprising the nine most important outcomes in bariatric and metabolic surgery clinical trials, including the hoped-for benefits as well as complications.
In collaboration with healthcare providers and patients who underwent bariatric surgery, lead author Karen D. Coulman, PhD, RD, of the University of Bristol in England, and colleagues, identified those outcomes that should be measured and reported for all trials.
The final COS criteria, published in PLOS Medicine, include:
- Weight trajectory.
- Diabetes status.
- Overall quality of life.
- Mortality (30-day and long-term).
- Technical complications of the specific operation.
- Any re-operation/re-intervention and its classification of severity.
- Micronutrient status.
- Cardiovascular risk.
Coulman and colleagues emphasized that the recommended COS is “not meant to be restrictive, rather the minimum that should be reported.”
Because the benefits and risks of the most common surgeries, including sleeve gastrectomy, Roux-en-Y gastric bypass, and adjustable gastric band, vary so greatly, the authors’ goal was to standardize the reporting of patient outcomes among clinical trials. As a result, they hoped to “improve the quality of data” as well as “reduce outcome reporting bias” in order to help healthcare professionals and patients make the most informed decision on their course of treatment.
The motivation was a “lack of consistency in outcome reporting, which hampered cross-study comparison and meta-analysis,” seen in previous studies and reviews.
The COS was developed through a set of three phases. The initial phase began with preliminary identification of a broad range of 2,990 potential items to consider in terms of patients outcomes following surgery. These items spanned 17 various domains, which were classified as a certain type of outcome, such as “obesity-related disease.” Phase 1 concluded with the development of a 130-item questionnaire.
Phase 2 involved the administration of a Delphi survey, including the questionnaire developed in the previous phase. The survey was initially provided to 258 healthcare professionals and patients who underwent bariatric surgery within the last five years. On a scale from 1 to 9 (1=not important, 9=extremely important to them), the participants ranked the proposed outcomes. This questionnaire was administered to the same participant group in three successive rounds, with some participants dropping out between rounds. The researchers calculated the median score for each item, and only retained the items that received a score of 8 or higher among 70% of participants. Following the conclusion of the third Delphi survey round, 35 of the most important outcomes were retained.
The final phase included face-to-face meetings in Bristol in the fall of 2015. These meetings utilized anonymous, keypad voting on the 35 criteria from the previous phase. Meetings for healthcare providers (n=33) and post-surgical patients (n=9) were held separately. While both participant groups largely agreed on the final nine COS criteria, “cardiovascular risk” was only voted in by healthcare professionals and not by the patient group.
Despite declining participation throughout each phase of the development, the recommended COS reflects a broad range of healthcare professional and patient opinions, Coulman and colleagues indicated.
“To our knowledge, this is the first study to develop a COS for bariatric surgery including professionals’ and patients’ views,” they wrote. The authors also noted that patients were surveyed a mean of 3.5 years after surgery, ensuring comprehensive experience of life afterward.
Coulman and colleagues did note that the study was only conducted in the U.K. and “few professionals from other countries participated,” limiting the generalizability of the outcomes. Building upon that notion, the authors discussed that their next steps are to “validate the COS internationally and determine how these outcomes are best measured.”