Urinary NGAL as an early marker of subclinical kidney injury in adults with substance use disorder: A case-control study.

Urinary neutrophil gelatinase-associated lipocalin (uNGAL) is a sensitive marker of tubular stress and injury that may detect early renal involvement before overt changes in conventional kidney function tests. This case-control study evaluated uNGAL as an early biomarker of subclinical kidney injury among adults with substance use disorder (SUD). Adults with SUD and no known kidney disease (n = 31) were compared with age-matched controls (n = 31). uNGAL was measured by ELISA together with serum creatinine and estimated glomerular filtration rate (eGFR; Cockcroft-Gault). uNGAL was markedly higher in participants with SUD than in controls (1913.1 ± 770.9 vs 71.5 ± 26.5 ng/mL; p < 0.001). Serum creatinine was higher, and eGFR was lower in the SUD group, although both remained within generally non-severe ranges. uNGAL demonstrated excellent discrimination between groups (AUC = 1.00; cutoff = 611.5 ng/mL; sensitivity and specificity = 100% in this sample). These findings suggest that uNGAL may reflect early or subclinical renal tubular injury in adults with SUD even when conventional renal markers show only limited changes. Larger prospective studies are needed to validate these findings and clarify prognostic utility.