Screening for proteinuria and hematuria in school children--methods and results.

In Japan, a urinalysis method in which the first morning urine sample is examined twice (Tokyo method) is currently widespread in the urine screening of school children. Mass screening of elementary school and junior high school children for urinary abnormalities using this method yielded a positive prevalence of proteinuria, hematuria and both abnormalities of approximately 0.08%, 0.5% and 0.03%, respectively, for elementary school children and corresponding values of approximately 0.4%, 0.9% and 0.08%, respectively, for junior high school students. These prevalence values may vary depending upon conditions of urine collection, conditions of preservation and transport of urine samples, time interval between collection and testing, testing facility, reagent strips and criteria for evaluation of test results. Since attempts at detection of renal disease through examination of urine tend to yield excess positive rates with an abundance of false-positives and false-negatives, the reliability of such testing is reduced unless it is performed correctly under strictly controlled conditions. In order to overcome these difficulties it is mandatory that the entire urinalysis system has a high degree of accuracy.