BACKGROUND: Programed death-ligand 1 (PD-L1) is overexpressed on renal tubular and vascular epithelial cells in inflammatory kidney diseases as well as on aged kidney podocytes, contributing to chronic kidney disease (CKD) progression. The association of serum soluble programed death-ligand 1 (sPD-L1) levels and chronic kidney disease (CKD) progression is unknown. METHODS: To compare serum sPD-L1 levels among healthy individuals and patients with various CKD stages, including those undergoing dialysis, a secondary analysis was performed using clinical data and residual serum samples from four distinct cohorts, each prospectively collected for different research purposes: The Vaccine Cohort (2021-2022), the Cancer Cohort (2010-2018), the Dialysis Initiation Cohort (2023-2024), and the Dialysis Maintenance Cohort (2011-2015) included patients on stable maintenance dialysis. RESULTS: The study analyzed serum sPD-L1 levels in 2,829 participants (mean age, 54.2 years
male, 54.2%) across the four cohorts. In the Vaccine and Cancer cohorts, sPD-L1 levels increased significantly with age ( CONCLUSION: Serum sPD-L1 levels might increase with CKD stage progression, dialysis initiation and longer dialysis duration. Further clinical investigation is required to confirm these results.