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Screening of proteinuria in a community-based population: General or Selective?
Chie Tomida, MD1, Fumiyo Watanabe, MD1, Hideto Takahashi, PhD2, Toshimi Sairenchi, PhD3 , Kumiko Ishida, MD4, Kunihiro Yamagata, MD1,
1Department of Nephrology, Institute of Clinical Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 2Department of Epidemiology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 3 Ibaraki Health Plaza, Ibaraki Health Service Association, 4Department of Health and Welfare, Ibaraki Prefectural Office

Background and objects:
To prevent an increase in the number of ESRD patients in Japan, universal screening of proteinuria has been available annually since 1972 under the auspices of local governments and the Ministry of Health, Labor and Welfare of Japan. However, universal screening for proteinuria was not performed in most countries, due to few cases of significant diseases had been detected with dipstick screening for proteinuria, and selectively directed toward high-risk groups or conducted at an infrequent interval of several years are recommended in USA and European countries. In this study, we try to investigate incidence of newly developed kidney damage (proteinuria) among general Japanese population and we try to find risk factors and effect of co morbid conditions on incidence of kidney damage among them.

Subjects and methods
The subjects were 123,764 (male: 41,012, female: 82,752) adults aged 40 and over who received community-based annual examinations in Ibaraki prefecture, Japan from 1993 to 2003. Patients with kidney damage were defined as follows; subject with no proteinuria at first year, and proteinuria of (+) or more at both consecutive second and third year was defined as kidney damage. We selected the subjects who received annual health checks three consecutive years during observation period and the several risk factors affecting the incidence of kidney damage were examined.

Results
The incidence of newly developing proteinuria among our population was 1.47% in male and 0.74% in female during the observation period.. Among the proteinuric subjects, 33.5% in male and 26.3% in female had proteinuria in the next year and the incidence of kidney damage was 0.59% in male and 0.25% in female. Among the patients with both diabetes and hypertension, incidence of kidney damage was 1.81% in male and 1.16% in female. Among the patients with hypertension only, incidence of kidney damage was 0.72% in male and 0.39% in female. Among the patients neither hypertension nor diabetes, incidence of kidney damage was 0.28% in male and 0.10% in female.

Conclusion
Incidence of newly developed proteinuria and kidney damage was very high in general Japanese subjects which was almost identical level in Caucasian hypertensive subjects, which was high-risk group. Annual screening for proteinuria in general Japanese adults is important to prevention for kidney damage and is highly cost-effective.

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