Comparison of urine collection methods for albuminuria assessment in young children

Abstract

Cotton wool or pantyliners placed in a diaper can be used as urine collection devices for albuminuria measurements in young, not continent children. We tested a new collection method (PeeSpot(R)) for its analytical performance, and compared it with the pantyliner technique. Eighty-one urine samples with a wide range of albuminuria were pipetted on the pantyliner and PeeSpot in duplicate. These were incubated for 3h at 37°C (simulating the time a toddler wears a diaper), and subsequently 72h at room temperature (simulating transport to a central laboratory). Urine was extracted by centrifugation and albumin concentration (UAc) was measured. UAC measured by the two methods was compared with UAC in an unprocessed reference aliquot stored for 75h at 4°C. Bias (mean percentage UAC difference between test and reference), precision (interquartile range of the UAC difference) and accuracy (proportion of samples within 30% of reference UAC) were calculated. Median UAC in the reference aliquot was 66.0mg/L [IQR 25.0-211.0], pantyliner 32.0mg/L [4.7-165.0; P<0.001 vs reference], and PeeSpot 61.0mg/L [27.0-216.0; P=0.84 vs reference]. Bias, precision and accuracy in pantyliner were -34.2%, 31.3mg/L and 48.1%; in PeeSpot 3.3%, 5.0mg/L and 96.3%. Passing-Bablok regression and Bland-Altman plot showed an underestimation for the pantyliner but not for the PeeSpot. The PeeSpot is an accurate and precise tool for collecting urine for albumin measurement in young children and should be preferred over the alternative cotton wool collection technique.

Keywords: Albuminuria; Pediatric nephrology; Urine collection methods.