Comparison of risks and costs of undiagnosed and diagnosed chronic kidney disease patients after the initiation of kidney replacement therapy in subsequent years. A Hungarian nationwide study.

INTRODUCTION

Despite high prevalence, chronic kidney disease (CKD) often remains undiagnosed and untreated, leading to an increased risk of end-stage kidney disease (ESKD), kidney replacement therapy (KRT), comorbidities, and premature death. In this retrospective nationwide study, we examined whether a lack of CKD diagnosis is associated with adverse post-KRT outcomes among newly dialyzed patients with chronic ESKD in Hungary.

METHODS

Two cohorts-undiagnosed (CKD naive) and diagnosed (CKD non-naive) patients (aged > 18 years)-were compared. Cohorts were defined based on pre-dialysis (>2 months) diagnosis-coding and erythropoietin therapy. We compared the risk of primary endpoints after KRT initiation (including all-cause mortality, acute myocardial infarction, stroke, hospitalization for heart failure (HHF), lower limb amputation (LLA), cancer, kidney transplantation) using propensity score subclassification for 56 confounders (matched data). We also examined exploratory endpoints (total healthcare costs, key comorbidities, laboratory testing, medications) over 5 years pre-KRT and/or post-KRT (unmatched data). Data were collected from the National Health Insurance Fund registry.

RESULTS

We identified 38,013 ESKD patients on KRT in 2009-2023, of whom 10,810 started dialysis in 2014-2018. Among these, 33% were undiagnosed (CKD naive). This group experienced more adverse events as early as 3 months post-KRT, including higher deaths (27% vs. 7.8%), HHF (18.8% vs. 11.1%), and cancers (11.2% vs. 2.1%). They also had fewer kidney transplantations (4.6% vs. 14%) at 72 months than the CKD non-naive group. Median survival was markedly shorter for CKD naive patients (3 months) than for CKD non-naive patients (34 months). Cox regression revealed higher risks for CKD naive patients for all-cause mortality [HR: 3.66 (CI: 3.12-4.29), p < 0.0001], cancers [HR: 3.31 (CI: 2.55-4.29), p < 0.0001], HHF [HR: 1.81 (CI: 1.55-2.11), p < 0.0001], stroke [HR: 2.27 (CI: 1.08-4.76), p = 0.0307], and LLA [HR: 2.17 (CI: 1.17-4.04), p = 0.0146] at 1 month post-KRT. Total costs rose 7.5-fold in undiagnosed CKD patients compared to a 4.5-fold increase in diagnosed CKD patients over 5 years pre-KRT, driven by higher hospitalization spending. Drug therapy costs were consistently higher in diagnosed vs. undiagnosed CKD patients pre-/post-KRT.

DISCUSSION: Undiagnosed CKD patients experience significantly worse outcomes post-KRT and incur higher long-term costs related to inpatient care. These findings underscore the need for early CKD diagnosis and timely interventions to improve survival and optimize healthcare resource utilization.