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.