Association between Time-Updated Eosinophil Counts and Progression of CKD

Abstract Patients with chronic kidney disease (CKD) have high blood eosinophil count but its clinical implication is uncertain. Since eosinophils may induce tubulointerstitial injury and arteriosclerosis, eosinophilia might be related to poor clinical outcomes. This retrospective cohort study included 2,877 patients whose estimated glomerular filtration rate (eGFR) was 10–60 mL/min/1.73 m2. The exposure was time-updated blood eosinophil counts. The outcomes were 1) initiation of renal replacement therapy (RRT) and 2) cardiovascular events and mortality. We analyzed the associations between eosinophil counts and outcomes using marginal structural models (MSM). Over a median follow-up of 6.5 years, eosinophil counts were measured a median of 22 times per patient (4 times a year per patient). There was a negative correlation between eosinophil count and eGFR. In total, 433 patients initiated RRT, 275 developed cardiovascular events, and 165 died. In MSM, higher eosinophil counts (≥ 289/µL) showed a 1.83-fold (95% confidence interval:1.33–2.51) higher rate of RRT initiation than lower eosinophil counts after adjustment for time-dependent confounders. Higher eosinophil counts were also associated with a higher rate of cardiovascular events and mortality in MSM (hazard ratio, 1.71 [95% confidence interval:1.30–2.25]). In conclusion, patients with CKD who had higher eosinophil counts showed worse kidney outcome.