Epidemiology of school urinary screening over a 30 year period in Tokyo

Background: A school urinary screening (SUS) system has been conducted for 30 years in Japan, but the cross-sectional data have never been reported or analyzed. The purpose of the present study was to analyze the data epidemiologically. Methods: All elementary and junior high school children in public school in Tokyo who had SUS performed by the Tokyo Health Service Association from 1974 to 2002 (approx. 400 000-600 000 children per year) were involved. The cross-sectional data were analyzed with Pearson's correlation coefficient. Results: During the first 10 years of SUS, the prevalence of abnormal urinalysis in both the first and second screenings varied widely, and the result of the second screening was affected by that of the first screening. The results of both first and second screening were highly correlated with the prevalence of hematuria, especially microhematuria, in both elementary and junior high school children. They were also correlated with the prevalence of proteinuria in junior high school children. Important factors that affected the prevalence of hematuria and/or proteinuria were reagent strips and sampling method of urinalysis. Conclusions: In order to validate SUS, attention should be paid to quality controls of the screening method, such as the selection of reagent strips, and the participants should be instructed to strictly adhere to the sampling method.