The risk of developing endemic nephropathy in subjects with proteinuria

Endemic nephropathy is a chronic tubulointerstitial disease characterized by early damage to the proximal tubule, with low-molecular weight proteinuria being an important hallmark and possible tool for early diagnosis. The aim of this retrospective cohort study was to assess the risk of developing endemic nephropathy in subjects with proteinuria from the endemic region in Croatia. The cohort study included subjects with proteinuria determined by the sulfosalicylic acid method (after 1988 with strip method), involved in the field survey conducted in the Croatian endemic village of Kaniza in 1975 and followed up until 1997. Subjects with endemic nephropathy established at the first visit and patients that failed to present for follow up visits after 1975. were excluded. In the field survey group that consisted of 624 subjects (286 male and 338 female), proteinuria was established in 157 subjects. Upon the application of exclusion and inclusion criteria, the study cohort included 111 of 157 subjects. The mean follow up was 7.26 years (95% confidence interval 4.06-10.46 years). During the follow up period, 19 (17%) subjects with initial proteinuria developed endemic nephropathy. The incidence density of endemic nephropathy among subjects with proteinuria was 1.3 per 100 persons/year. Estimated risk was 0.0137 (confidence interval 0.0087-0.0214) per year of exposure. The presence of proteinuria determined by the sulfosalicylic acid or test strip in subjects from the endemic village indicated that endemic nephropathy would develop in 1.3 of 100 subjects with proteinuria per year.