Identification of children with chronic kidney disease through school urinary screening using urinary protein/creatinine ratio measurement: an observational study.

School urinary screening has been performed in Japan. Ikeda City and Toyono Town introduced, in 2012 and 2013, urinary protein/creatinine (Cr) ratio measurement into the urine-screening protocols designed for students aged between 4 and 15 years. For each student whose urinary protein/Cr ratio was ≥ 0.15 g/gCr (positive case), an appointment was made with a specialist at Ikeda City Hospital. The results of these screening urinalyses conducted through 2018 are summarized. 14,606 junior high and elementary school students aged between 6 and 15 years were included. On average, they underwent 4.16 screening tests. 77 positive cases were detected, and seven students were diagnosed with high-risk chronic kidney disease (CKD). Of these, four underwent renal biopsy, and two, one, and one were diagnosed with IgA nephropathy, MPGN, and FSGS, respectively. In three students, detection of CKD would have been difficult without urinary screening. Incident rates of high-risk CKD and IgA nephropathy are estimated as 11.5 and 3.3 cases/100,000 students/year. 78.0% of positive cases without high-risk CKD showed no urinary abnormality after one year. 2301 kindergarten students aged between 4 and 6 years received an average of 1.74 screening urinalyses; none was positive or high-risk CKD. The estimated cost of detecting one high-risk CKD student whose detection would have been difficult without this screening was 3,156,711 Japanese yen. School urinary screening using the urinary protein/Cr ratio can efficiently refer to a specialist. It detects a few children with high-risk CKD early with spending high cost.