Quantification of Urinary NGAL Using Volumetric Dried Urine Sampling

Objective: To evaluate the measurement of urinary neutrophil gelatinase-associated lipocalin (NGAL) from dried urine samples collected using Capitainer qDBS discs compared with liquid urine. Methods: Eighty urine samples from children aged 0-18 years were analysed. NGAL concentrations measured in liquid urine were compared with concentrations obtained from dried urine collected on Capitainer qDBS cards and eluted for analysis using a commercial ELISA. Method agreement was assessed using linear regression and Bland-Altman analysis. Results: Sixty-nine samples yielded measurable NGAL concentrations in both methods. Median NGAL concentrations were 8.72 ng/mL (IQR 3.97-20.88) in liquid urine and 8.48 ng/mL (IQR 3.28-20.11) in qDBS eluates. NGAL concentrations measured from qDBS correlated with liquid urine measurements with a strong linear relationship (R² = 0.98). Method agreement was good. Median recovery of 95.4% indicated slightly lower concentrations in qDBS eluates. Conclusions: NGAL measurements obtained from volumetric dried urine sampling using Capitainer qDBS discs showed good agreement with liquid urine measurements.