We reexamined the cases of renal disease found in urinalyses which had been performed as part of the mass screening, to ascertain its efficacy. During 1990, a total of 94, 913 people underwent physical checkups made by the Naganoken Kouseiren Health Screening Center. The mean positive rates of proteinuria, occult blood in urine and both were 2.4%, 6.2% and 0.5%. Of the total number of examinees, 59, 803 had undergone the previous year's checkup. The mean positive rates of proteinuria, occult blood in urine and both for two consecutive years were 0.8%, 3.4% and 0.1%. The mean positive rates of proteinuria and occult blood increased with age. The mean positive rate of proteinuria was 1.7 times higher in males than in females. On the other hand, the mean positive rate of occult blood was 2.7 times higher in females than in males. However, there was no difference what so ever between men and women in the mean positive rate of both proteinuria and occult blood.
In the mean time, we reviewed the 85 cases in which renal biopsy was performed at the Saku Central Hospital from 1985 through 1990. Among them, 35 (41.2%) were the cases which had been suspected to have kidney disorder in the urinalysis conducted as part of a mass screening, and IgA nephropathy accounted for about 60% of them. The reports from medical institutions which made follow up examinations using the results of the health screening showed that the rate of renal disease was highest in the proteinuria positive cases; that of urological diseases, in the occult blood positive cases; that of chronic glomerulonephritis and urological diseases, in the proteinureal occult blood positive cases. We concluded that urinalysis included in a battery of tests at the time of the mass health screening is an effective procedure for detecting chronic glomerulonephritis and urological diseases.