Defining delayed graft function in kidney transplantation: A scoping review of outcome reporting practices

Delayed graft function (DGF) is a commonly reported outcome in kidney transplantation research, but no single definition has been uniformly adopted. Variation in how DGF is defined, measured, and analysed may limit evidence synthesis, and affect trial design. We conducted a scoping review to map contemporary DGF outcome reporting practices in adult kidney transplantation.

We conducted a scoping review using the Arksey and O'Malley framework, reported in accordance with PRISMA-ScR. MEDLINE and Embase were searched for English-language studies published from 1 January 2009 onwards. Eligible adult kidney transplant studies reported DGF as an outcome and explicitly defined it. Data were charted on study characteristics, definition type, timing, aggregation, justification, and analysis. Because some studies reported more than one definition, the unit of analysis was the individual DGF definition.

261 included sources yielded 305 DGF definitions, with 88 definitional variants across 5 main definitional families. 60 full-text records were excluded because they used DGF as an outcome without definition. Dialysis-within-7-days predominated, which accounted for 44% of definitions. Alternative dialysis-based definitions accounted for 18%, duration- or severity-stratified definitions for 21%, creatinine-based definitions for 9%, and composite clinical definitions for 9%. The first post-transplant week was the dominant time frame. Most definitions were binary (98%). Justification for authors' chosen definition was absent in 41%.

Contemporary DGF reporting is dominated by binary dialysis-based definitions despite the biological and clinical heterogeneity of DGF. A standardised research endpoint designed according to a novel framework may improve validity, comparability, and future trial design.