#717 Recipient/donor characteristics and immunosuppression impact eGFR creatinine and creatinine-cystatin c equations in kidney transplant recipients

Background and Aims Previous studies have shown substantial heterogeneity in the performance of estimated glomerular filtration rate (eGFR) equations when applied to kidney transplant recipients (KTRs). The impact of transplantation-related characteristics on eGFR equations based on creatinine (eGFRcr) compared with creatinine and cystatin C (eGFRcr-cys), however, remains insufficiently studied. Method We analyzed 596 KTRs transplanted at the University Hospital Zurich. The accuracies of four eGFRcr equations (CKD-EPI 2009 and 2021, EKFC 2021, KRS-GFR 2023) were compared with three eGFRcr-cys (CKD-EPI 2012 and 2021, EKFC 2023), and evaluated across a detailed range of transplantation-related variables. Performances were assessed using bias, P30, P20 and correct classification (CC). Multivariate analysis identified transplantation-related characteristics independently associated with a smaller or greater difference between eGFRcr and eGFRcr-cys equations. Results Based on eGFRcr-cys CKD-EPI 2012 as the reference, CKD-EPI 2021 (P30: 77.0%, P20: 56.4%, CC: 56.4%) and KRS-GFR 2023 (P30: 80.2%, P20: 64.9%, CC: 60.1%) had lower performance, while EKFC 2021 (P30: 88.6%, P20: 75.8%, CC: 66.8%), and CKD-EPI 2009 (P30: 87.1%, P20: 70.3%, CC: 64.6%) showed higher performance. Belatacept use was associated with a smaller difference between eGFRcr CKD-EPI 2009 and eGFRcr-cys CKD-EPI 2012 (OR 3.295, 1.605-6.764, p = 0.001), while a higher donor BMI was associated with a greater difference between eGFRcr KRS-GFR 2023 and eGFRcr-cys CKD-EPI 2012 (OR 1.077, 1.001-1.158, p = 0.046). Conclusion More recent eGFRcr equations do not overcome the limitations of non-GFR determinants of creatinine in KTRs, however European equations seem to be equally feasible in transplanted patients. Transplantation-related characteristics of the recipient, donor, and immunosuppressive medication affect the differences between eGFRcr and eGFRcr-cys, which needs attention in clinical practice.