A prospective study of the association between plasma calprotectin levels and new-onset chronic kidney disease in the general population

Introduction
Systemic inflammation has been associated with chronic kidney disease (CKD). In this study, we aimed to investigate a potential association between the plasma biomarker of inflammation calprotectin and new-onset CKD in a population-based cohort study.

Methods
Individuals without CKD at baseline (n=4,662) who participated in the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) prospective population-based cohort study in the Netherlands were included. Baseline plasma calprotectin levels were assessed in samples that had been stored at -80°C. Occurrence of new-onset CKD was defined as a composite outcome of an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73m2, urinary albumin excretion (UAE) >30 mg/24-h, or both.

Results
Baseline median [IQR] plasma calprotectin levels were 0.49 [0.35-0.68] mg/l and baseline median eGFR was 95.9 [IQR: 85.0-105.7] ml/min/1.73m2. After median follow-up of 8.3 [7.8-8.9] years, 467 participants developed new-onset CKD. Baseline plasma calprotectin levels were significantly associated with an increased risk of new-onset CKD (hazard ratio [HR] per doubling 1.28 [95% CI: 1.14-1.44], P<0.001), independent of potentially confounding factors (HR 1.14 [95% CI: 1.01-1.29], P=0.034), except for baseline hs-CRP (HR 1.05 [0.91-1.21], P=0.494). In secondary analyses, the association between plasma calprotectin and occurrence of UAE >30 mg/24-h remained significant (HR 1.17 [1.02-1.34], P=0.027), but not significantly so for the incidence of eGFR <60 ml/min/1.73m2 as individual outcome (HR 1.15 [0.92-1.43], P=0.218).

Conclusion
Higher plasma calprotectin levels are associated with an increased risk of developing CKD in the general population. This association is mitigated after adjustment for hs-CRP, and more pronounced with new-onset CKD defined by UAE.