CKD stage-to-stage progression in native and transplant kidney disease

Background. Kidney half-life and inter-stage progression rates in native chronic kidney disease (CKD) and CKD-transplant (CKD-T) remain unknown. Methods. We examined stage-to-stage progression/regression rates in patients with CKD (n = 601) and CKD-T (n = 431) between 1991 and 2001. Kidney function was estimated by CockcroftGault and MDRD eGFR formulae. KaplanMeier analyses determined progression and regression half-lives, defined as the time required for 50% of kidneys to advance towards a higher or lower stage of CKD, respectively. Results. Most (67%) of the patients were in stage 3. Patients with native CKD were more likely to progress compared to CKD-T (inter-stage progression rates 12 vs 4 cases per 100 patient-years, P < 0.0001). Accordingly, estimated glomerular filtration rate (eGFR)-based progression half-lives were significantly shorter in CKD compared to CKD-T [6 vs 9.6 years, P < 0.0001, hazard ratio (HR) 3.1, 95 confidence interval (CI) 2.53.7]. Creatinine clearance (CCR)-based stage half-lives were 7.2 months shorter in each group (5.4 and 9 years in CKD and CKD-T, respectively). Despite slower progression rates in patients with transplant kidney disease, adjusted patient survival rates were significantly decreased in CKD-T compared to CKD. Only Scr and CCR-based formulae were significantly associated with patient and allograft outcomes in the CKD-T group. Moreover, death rates were not different in stage 3 compared to stage 2 CKD-T, suggesting that eGFR and the current staging classification have a limited value to predict patient death in this cohort. Conclusion. Kidney half-lives per stage of CKD may be a novel tool to examine disease progression.