Balkan endemic nephropathy (BEN) is a chronic kidney disease that progresses
slowly. There are no known clinical markers to identify an early disease development. We evaluated
the relationship between parental history of BEN and clinical markers as predictors of new
occurrences of BEN. A 5-year prospective study in the offsprings of BEN and control patients
was conducted in Vratza, Bulgaria, between 2003 and 2009 using markers in years one and three
to predict new cases of BEN in the year five. We defined incident cases of BEN based on parental
history, reduced kidney size and reduced kidney function, distinguishing probable and definite
BEN, both combined as total incidence. The data were analyzed by Cox regression models using
age as time scale and controlling for gender. We estimated hazard ratios and their 95% confidence
intervals. The incidence of BEN was 17.4%. Paternal history was strongly associated with all
three incidence groups (hazards ratio: 27–68, P