Discussion
AKI
This is a post hoc analysis of a multicenter randomized trial investigating recent evidence of an association between low penKid values with early and successful CRRT liberation. This association was reproducible in this external cohort, however with limitations. First, the effect was only present during CRRT, but not at baseline. We hypothesize that the initiation time point influences the predictive value of the biomarker. In the RICH trial, CRRT was initiated in patients with more severe AKI (KDIGO stage 3 or absolute indication), compared to the ELAIN trial (KDIGO stage 2). This is also reflected in the higher median penKid in the RICH cohort (134.18 pmol/l), compared to the ELAIN cohort (106.95 pmol/l) at baseline.Second, a slightly higher cutoff value to distinguish groups was more appropriate. This might be due to differences in patient populations: The RICH study investigated a mixed patient population, including surgical and non-surgical patients, while the ELAIN trial only included surgical patients Higher penKid levels in non-surgical patients are also in line with previous studies [Our study has several limitations, such as the retrospective study design and the relatively low rate of samples available at landmark analysis. Furthermore, the study protocol did not standardize termination of CRRT. Our results suggest that penKid may identify patients with higher chances of successful liberation from CRRT, however appropriate urinary output (> 436 ml/d) outperformed penKid. Data did not suggest a relevant imbalance between randomization groups (heparin or citrate anticoagulation) and penKid group.Overall, this study emphasizes the potential of penKid to identify patients for CRRT liberation as it may assess kidney function even during CRRT. Moving forward, a prospective study is required.