Danica Bukvić

Prevalence of Balkan Endemic Nephropathy Has Not Changed Since 1971 in the Kolubara Region in Serbia

Background/Aims: Thirty-one years after the first cross-sectional study, the population of Vreoci, a Balkan endemic nephropathy (BEN) village, was reinvestigated in order to determine the current prevalence of BEN and the clinical and laboratory characteristics of BEN family members with detected signs of kidney disease. Methods: A total of 2,009 inhabitants (82% of the adult population) of the village were examined. Danilovic’s criteria were used for diagnosis and classification of BEN. Results: The prevalence of BEN (1.70%) was similar to that in 1971 (1.67%). Diagnosis of BEN was established in 19 BEN family members, suspected BEN in 23, proteinuria in 29, while 16 healthy members were examined as controls. Urine protein, alpha1-microglobulin levels and frequency of glucosuria were significantly higher and kidney length significantly smaller in the three patient groups than in healthy persons. Serum urea and creatinine levels were significantly higher, but creatinine clearance was lower in BEN and BEN suspected patients than in the other two groups. Conclusion: The prevalence of BEN remains stable over time in Vreoci village. Manifested disease was found in both BEN and BEN suspected patients. In persons with proteinuria but not enough criteria for BEN, tubular disorders and hypertension were frequently found.

Detection of Renal Dysfunctions in Family Members of Patients with Balkan Endemic Nephropathy

Background/Aim: Recent studies have questioned whether new cases of Balkan endemic nephropathy (BEN) are occurring. The aim of the present study was to find out whether new members with renal dysfunctions can be identified among family members of BEN patients from the Kolubara region. Methods: The study included 47 family members of 5 BEN patients on hemodialysis (HD) and 17 members of 3 non-BEN patients on HD. Their medical and epidemiological histories were taken, an objective survey made, and all persons were examined for global and tubular kidney function. Results: Seven BEN family members (2 with previously known BEN) had creatinine clearance (Ccr) below the 75th percentile rank according to sex and age. All non-BEN family members had normal Ccr and no evidence of previous renal disorders. Hypertension was found in 20 (43%) BEN and 6 (35%) non-BEN family members. No significant differences in the frequency of renal function disorders (proteinuria, α1-microglobulinuria, urine specific gravity, osmolality, functional excretion of sodium, tubular phosphate resorption) or anemia were found between the groups. Renal disorders were detected in 18 BEN family members without previously detected disease, 3 of whom fulfilled criteria for a diagnosis of BEN and another 2 for BEN-suspected persons. Conclusion: New cases of BEN are still arising among the affected families in the Kolubara region.

Contribution to the definition of diagnostic criteria for Balkan endemic nephropathy

BACKGROUND Diagnostic criteria for Balkan endemic nephropathy (BEN) have not been precisely established. In the present study the predictive value of variables previously proposed as diagnostic criteria for BEN was examined. METHODS The study involved 182 patients: 98 patients with BEN, 57 patients with other kidney diseases (20 with glomerulonephritis, 17 with tubulointerstitial diseases and 20 with hypertensive nephrosclerosis) and 27 healthy subjects. The BEN group comprised patients who fulfilled criteria for BEN and suspected BEN, together with patients with proteinuria and at least two tubular abnormalities or one tubular abnormality and a history of urothelial tumour. Demographic, clinical, laboratory and ultrasound variables of examined groups were combined in univariate/multivariate logistic regression analysis. RESULTS Out of 28 analysed variables only urine alpha1-microglobulin (MG) and kidney length were selected as significant predictors in differentiating BEN from other kidney diseases and healthy controls. Using ROC curves the cutoff values of these variables and proteinuria and kidney volume, variables collinear with them, were found. Moderate sensitivity and specificity characterized all these cutoff values except for proteinuria, which provided high sensitivity and specificity in combination of BEN and healthy persons. The predictive value of different combinations of selected variables was not significantly different from the predictive value of each variable individually. CONCLUSIONS Proteinuria, urine alpha1-MG, kidney length and volume were selected as significant predictors of BEN. Variables related to kidney failure as well as several tubular disorders (urine specific gravity, FENa and TRP) had an insignificant predictive value and could not be used for differential diagnosis of BEN.

Beta2-Microglobulin and Alpha1-Microglobulin as Markers of Balkan Endemic Nephropathy, a Worldwide Disease

Background: Urine beta2-microglobulin (beta2-MG) was mainly used as a tubular marker of Balkan endemic nephropathy (BEN) but recently alpha1-microglobulin (alpha1-MG) was proposed for the diagnosis of BEN. In this study, the potential of urine beta2-MG, alpha1-MG, albumin, and total protein in the differentiation of BEN from healthy persons and patients with glomerulonephritis (GN) and nephrosclerosis (NS) was examined. Methods: This study involved 47 patients with BEN, 36 with GN, 11 with NS, 30 healthy subjects from BEN families, and 46 healthy subjects from non-BEN families. Results: In BEN patients area under the curve (AUC) for urine beta2-MG (0.828) and alpha1-MG (0.782) was higher than for urine albumin (0.740), but in GN patients AUC for urine protein (0.854) and albumin (0.872) was significantly higher than for the two low molecular weight proteins. AUC for all four urinary markers in NS patients was significantly lower than in BEN patients, ranging between 500 and 595. Median urine beta2-MG excretion in BEN patients was 17.5 times higher than in GN patients and 18.3 times higher than in controls; median alpha1-MG excretion was higher only 3.0 and 2.25 times, respectively. In the differentiation of BEN from healthy controls, beta2-MG had higher sensitivity and specificity at the cutoff levels (p < 0.001) than alpha1-MG (p < 0.05). In the differentiation of BEN from GN, beta2-MG was the best marker. Conclusion: All four urinary markers can be used for the differential diagnosis of BEN, beta2-MG being the best. Like in aristolochic acid nephropathy, beta2-MG seems to be an early marker of tubular damage in BEN.

Time trends in Balkan endemic nephropathy incidence in the most affected region in Serbia, 1977–2009: the disease has not yet disappeared

BACKGROUND Balkan endemic nephropathy (BEN) is a familial chronic kidney disease, which occurs only in some regions of the Balkan Peninsula. The aim of this study was to determine the main epidemiological features of BEN in the Kolubara region, the most affected region in Serbia, and to try to elucidate the controversial issue of whether or not BEN is tapering off. METHODS To evaluate the BEN incidence rates in the municipality of Lazarevac over a 33-year period (1977-2009), we used data of BEN notifications from the BEN Registry located in the Special Hospital for Endemic Nephropathy, Lazarevac. Population data were obtained from the 1981, 1991 and 2002 national censuses by interpolation. BEN incidence rates were standardized according to the European standard population, and their trends were assessed by Poisson regression model and joinpoint analysis. RESULTS The age-adjusted BEN incidence rates combined for both sexes over a 33-year period (1977-2009) fitted a significant quadratic (U-shaped) trend (y = 58.44 - 3.76 + 0.10x(2), P = 0.026). Joinpoint analysis showed that the overall age-standardized BEN incidence rates significantly decreased in the first decade of the observed period (1977-89) by an average of 10.0% annually, while a nonsignificant increase of 3.9% per year was recorded in the last two decades (1989-2009). CONCLUSIONS Our results revealed that BEN still exists in the Kolubara region. The predicted disappearing scenario of this still mysterious disease has not happened.

Balkan Endemic Nephropathy is Still Present in the Kolubara Region, Serbia

Background. Almost 50 years ago Balkan Endemic Nephropathy (BEN) was first described in Serbia in the village of Šopić where the first field examination was carried out in 1971. Our aim was to find out whether BEN is still present in this region. Methods. Prevalence data on BEN from a field examination run in 1971 were compared with the results of a cross-sectional study conducted in the same village in 1992. In addition, every new case of the disease diagnosed between 1971 and 1992 was recorded retrospectively. The prospective study included 50 members of five BEN families randomly selected from 28 BEN families registered in the village Šopić in 1992. The objective survey and examination of global and tubular kidney function was carried out in all examined persons once yearly in 1998, 1999, and 2000. Results. The overall prevalence of BEN was 6.4% in 1971 and 8.9% in 1992. In the period of 21 years, 161 new BEN patients were detected in 28 families in which the disease had already been recorded. No new family affected by BEN and none of the new patients in 47 families registered previously as nonaffected were discovered. In the prospective study of five BEN families, three new BEN cases were discovered among 50 members, and two patients fulfilled criteria for BEN-suspected ones. Conclusion. Balkan Endemic Nephropathy (BEN) is still present in the village of Šopić, but the clinical course of the disease became more protracted over time. New cases of BEN appeared only in the affected families.

Evaluation of Criteria for the Diagnosis of Balkan Endemic Nephropathy

Background. The diagnosis of Balkan endemic nephropathy (BEN) is often made using Danilovics criteria. The aim of this study was to determine the prevalence, sensitivity, specificity, and predictive value of Danilovics criteria and several additional indices. Methods. The study included 19 BEN patients, 23 BEN-suspected patients, 34 patients with other kidney diseases, and 23 healthy controls. The sensitivity and specificity of Danilovics criteria was calculated, and these criteria, in addition to age, sex, blood pressure, creatinine clearance, glucosuria, urine osmolality, alkaline phosphatase, alpha 1-microglobulin, fractional sodium excretion, tubular phosphate reabsorption, kidney length, and volume, were combined in a logistic regression. Results. All examined persons were from a BEN-affected village (criterion 1), and all BEN, BEN-suspected patients, and 12/23 healthy controls were from BEN families (criterion 2). None of the remaining Danilovics criteria was found in the healthy controls. The prevalence of proteinuria, low specific gravity, and anemia (criteria 3–5) differed insignificantly among the patient groups. Azotemia and shrunken kidney (criteria 6 and 7) were significantly more frequent in BEN than in other patients. Only proteinuria showed high sensitivity and specificity in differentiating BEN and BEN-suspected patients from healthy persons, but no criteria differentiated BEN or BEN-suspected from other kidney diseases. Proteinuria is a significant predictor of both BEN and BEN-suspected vs. healthy persons, and alpha 1-microglobulinuria is a significant predictor of BEN vs. other kidney diseases. Conclusion. Danilovics criteria enabled a diagnosis of BEN only in chronic renal failure and differential diagnosis between BEN and healthy persons but not between BEN and other kidney diseases. Out of the examined indices of proximal tubular disorders, only alpha 1-microglobulinuria significantly discriminated BEN from other kidney diseases.

Screening of a Population at Risk of Chronic Kidney Disease: Analysis of Factors Associated with Low eGFR and Microalbuminuria

Background and objective: Numerous screenings of chronic kidney disease (CKD) have been performed all over the world. This screening study was undertaken with the aim of estimating the prevalence of low glomerular filtration rate (eGFR) and microalbuminuria (MAU) and/or proteinuria in a population at risk for CKD and to detect factors associated with these CKD markers. Materials and methods: This cross-sectional study included 1617 patients without previously known kidney disease who came for regular check-ups to their general practitioners in 13 Belgrade health centers over a 3-month period. Patients selected were as follows: 1316 with hypertension, 208 with type 2 diabetes, and 93 older than 60 years without hypertension or diabetes. Screening included a questionnaire, blood pressure measurement, single MAU dipstick measurement (Micral-test® strip) and proteinuria and GFR estimation by Modification of Diet in Renal Disease. Results: MAU was found in 419 (25.9%) patients, proteinuria in 163 (10.1%), and eGFR < 60 mL/min/1.73 m2 in 370 (22.9%). Multivariate logistic regression analysis revealed that female gender, age, duration of hypertension, and smoking were associated with eGFR. Male gender, hypertension, treatment with angiotensin-converting enzyme inhibitors, proteinuria, and systolic blood pressure were associated with MAU. Conclusions: High prevalence of MAU/proteinuria and reduced eGFR were found in high-risk persons for CKD. Besides nonmodifiable, significant modifiable factors for MAU were use of angiotensin-converting enzyme inhibitors and strict regulation of hypertension and the factor for reduced eGFR was smoking.

Transforming Growth Factor-β1 in Balkan Endemic Nephropathy

Background/Aim: The aim of this study was to compare plasma and urine transforming growth factor-β1 (TGF-β1) levels in patients with different stages of Balkan endemic nephropathy (BEN) with those in patients with primary glomerulonephritis (GN) and healthy controls. Methods: The study involved 47 patients with BEN (30 with manifest BEN and 17 in the early stage of BEN), 12 patients with GN and 10 healthy controls. Plasma and urine TGF-β1 was assayed by enzyme-linked immunosorbent assay. Results: The median plasma TGF-β1 levels differed nonsignificantly between the groups (4,908–6,442 pg/ml), but individual plasma TGF-β1 levels in BEN patients exhibited the highest dispersion. Median urinary TGF-β1 excretion (pg/mg creatinine) was significantly higher in patient groups (manifest BEN: 203, early-stage BEN: 341, GN: 775) than in healthy controls (42). No correlation was found between plasma and urine TGF-β1 levels or between plasma TGF-β1 levels and creatinine clearance for any of the examined groups. Conclusion: Plasma TGF-β1 levels in BEN patients extended over the widest range, but no significant differences were found between the median values for the groups. Median urinary TGF-β1 excretion was significantly higher in patients with BEN and GN than in healthy controls.

Trends in Incidence and Prevalence of Balkan Endemic Nephropathy in the Three Most Affected Villages in Serbia Over a 36-Year Period

The study was undertaken with the aim to evaluate trends in incidence and prevalence of Balkan endemic nephropathy (BEN) in the villages Šopić, Petka, and Vreoci, Lazarevac municipality, Serbia. Data concerning BEN notifications in the population-based registry of the Special Hospital for Endemic Nephropathy, Lazarevac were used to evaluate BEN incidence rates in the three villages over the period 1973−2008. Population estimates were based on national census data. All age-adjusted incidence rates were standardized to the European standard population and trends were assessed by Poisson regression model and joinpoint analysis. The prevalence of BEN was obtained in cross-sectional studies carried out in the villages Šopić (1971 and 1992), Vreoci (1971 and 2002), and Petka (1971 and 2008). The overall age-standardized incidence rates of BEN in the three villages changed over time. The significant 8.6% annual decrease in the first 16 years of the observed period was followed by a slight increase of 4.6% annually in the last two decades. The age-standardized incidence rates changed over time, being the greatest in the years when the field investigations were made. There was an insignificant change in BEN prevalence in Šopić and Vreoci and a significant decrease in prevalence in Petka. During a 36-year period, 367 new cases of BEN were registered in the three endemic villages and the overall age-standardized incidence rate varied over time. As BEN is a slow-progressing and asymptomatic chronic kidney disease, early detection of BEN can only be achieved by field examination.