Urine concentration adjustment with a dipstick is dispensable for urinary beta 2-microglobulin screening in children

Single voided urine was collected from 1,699 3-year-olds. The urinary beta 2-microglobulin levels (microgram/l) were measured by ELISA. The frequency of the levels was distributed with a wide base on the right side, even after logarithmic transformation. The upper limits of the 98% confidence interval were 660 micrograms/l for boys and 690 micrograms/l for girls. The values adjusted to a specific gravity of 1,020 in a total of 1,468 urine samples, of which the specific gravity was examined with Nephrosticks L, from 746 boys and 722 girls were similarly distributed, and the upper limits of the 98% confidence interval were 550 micrograms/l for boys and 530 micrograms/l for girls. There was no significant sex-related difference. Of the 14 children who had adjusted beta 2-microglobulin values above the adjusted upper limit of the 98% confidence interval, 11 (79%) had actual levels above the actual upper limit of the 98% confidence interval, 11 (79%) had actual levels above the actual upper limit of the 98% confidence interval. Finally, 2 children (one boy and one girl) proved to have renal disease. In these 2, both the actual and adjusted values exceeded the respective upper limits of the 99% confidence interval. Concentration adjustment appears to be dispensable in the screening for renal disease. In practice, 600 micrograms/l would serve as an actual cut-off level for both sexes with safety.