Proenkephalin A 119–159 predicts early and successful liberation from renal replacement therapy in critically ill patients with acute kidney injury: a post hoc analysis of the ELAIN trial

Abstract Background Renal replacement therapy (RRT) remains the key rescue therapy for critically ill patients with severe acute kidney injury (AKI). However, there are currently no tools available to predict successful liberation from RRT. Biomarkers may allow for risk stratification and individualization of treatment strategies. Proenkephalin A 119–159 (penKid) has been suggested as a promising marker of kidney function in the context of AKI, but has not yet been evaluated for RRT liberation in critically ill patients with AKI. Methods This post hoc analysis included 210 patients from the randomized clinical ELAIN trial and penKid levels were measured in the blood of these patients. Competing risk time-to-event analyses were performed for pre-RRT penKid at initiation of RRT and in a landmark analysis at day 3 after initiation of RRT. Competing risk endpoints were successful liberation from RRT or death without prior liberation from RRT. Results Low pre-RRT penKid levels (penKid ≤ 89 pmol/l) at RRT initiation were associated with early and successful liberation from RRT compared to patients with high pre-RRT penKid levels (subdistribution hazard ratio (sHR) 1.83, 95%CI 1.26–2.67, p = 0.002, estimated 28d-cumulative incidence function (28d-CIF) of successful liberation from RRT 61% vs. 45%, p = 0.022). This association persisted in the landmark analysis on day 3 of RRT (sHR 1.78, 95%CI 1.17–2.71, p = 0.007, 28d-CIF of successful liberation from RRT 67% vs. 47%, p = 0.018). For both time points, no difference in the competing event of death was detected. Conclusions In critically ill patients with RRT-dependent AKI, plasma penKid appears to be a useful biomarker for the prediction of shorter duration and successful liberation from RRT and may allow an individualized approach to guide strategies of RRT liberation in critically ill patients with RRT-dependent AKI. Trial registration: The ELAIN trial was prospectively registered at the German Clinical Trial Registry (Identifier: DRKS00004367) on 28th of May 2013. Graphical Abstract