Analyte variations in consecutive 24-hour urine collections in children

Our analysis indicates that stone risk in as many as one in four children may be misclassified if normative values of only a single 24-h urine are used. In light of these findings, repeat 24-h urine collections prior to targeted intervention to modify stone risk are advised to increase diagnostic yield in children at risk for nephrolithiasis.Table. Percent variability and discordant samples (based on normative thresholds) for urinary parameters in consecutive 24-h urine studies in children.ParameterPercent variabilityDiscordant samples≥30%≥50%Calcium (N, %)219 (34.2)102 (15.9)88 (13.1)Oxalate (N, %)94 (23.3)28 (6.9)104 (22.5)Citrate (N, %)92 (16.6)22 (4.0)42 (8.2)SS CaOx (N, %)N/AN/A138 (20.5)SS CaPhos (N, %)N/AN/A169 (25.1)Volume269 (36.8)89 (12.2)N/A