Urinary presepsin is a novel biomarker capable of directly assessing monocyte/macrophage infiltration in kidney diseases.

Serum presepsin levels are elevated during sepsis and are widely employed in clinical practice. However, the association between urinary presepsin and kidney diseases remains elusive. Given that monocytes/macrophages, primary presepsin producers, are closely associated with the pathophysiology of nephritis, we explored the potential of urinary presepsin as a kidney disease biomarker. In a cross-sectional study involving patients who underwent kidney biopsy (n = 463 patients; 43% female, median age 58 years), the median urinary presepsin/creatinine levels were 590 (interquartile range [IQR], 244-1276), 1023 (IQR, 491-2749), 1429 (IQR, 644-2725), and 3518 (IQR, 2084-6321) ng/g creatinine, indicating minimal (< 5%), mild (5-25%), moderate (26-50%), and severe (> 50%) interstitial inflammatory cell infiltration in biopsy samples, respectively. The area under the curve of urinary presepsin/creatinine (0.81) had a higher accuracy for distinguishing severe interstitial inflammatory cell infiltration than that of the N-acetyl-β-D-glucosaminidase/creatinine (0.70) (P = 0.003). The tubulointerstitial nephritis group had the highest urinary presepsin/creatinine level. Immunofluorescence staining revealed that monocytes and macrophages predominantly expressed presepsin in the kidney interstitium, with the stained area positively and significantly correlated with presepsin/creatinine values (r = 0.57, P = 0.02). Urinary presepsin could be a biomarker for directly assessing monocyte/macrophage infiltration in kidney disease.