Antibodies to Tamm-Horsfall protein in endemic nephropathy.

BACKGROUND: The aim of the study was to investigate the possible role of antibodies to Tamm-Horsfall protein (anti-THP) in the early diagnosis of endemic nephropathy (EN). METHODS: Anti-THP (IgA, IgM, IgG classes) antibodies were determined by direct ELISA in a random sample of 159 subjects from the endemic village of Kaniza who were divided into four groups according to the WHO criteria, i.e., 'diseased', 'suspect', 'at risk', and 'others'. These groups were compared to subjects from the non-endemic village of Klakar and healthy subjects from Zagreb. RESULTS: No differences for all the classes of antibody were observed among the groups of subjects from the endemic village of Kaniza (P>0.05) or between these subjects and those from the non-endemic village of Klakar (P>0.05). The values of IgM anti-THP antibodies exceeded those of the IgA and IgG classes in all groups of subjects (P<0.05). The values for all three classes of antibodies were higher in the rural than the urban population (P<0. 05). CONCLUSION: Determination of anti-THP antibodies was not found to be useful in the early diagnosis of endemic nephropathy. The results suggest that most of the anti-THP antibodies are 'natural' and/or cross reactive. The highest values observed in the rural population could probably be explained by exposure to some ubiquitous antigen or more likely they are consequences of fever.

Endemic nephropathy in Croatia.

Endemic nephropathy is a chronic renal disease with a high prevalence in a geographically limited area of Croatia. It has also been recorded in some parts of Bosnia, Serbia, Bulgaria and Romania. Despite numerous studies conducted to date, the etiology of this disease has not been clarified. Pathological studies of the kidney in the early stage of endemic nephropathy have shown renal tubules to be the primary sites of the pathologic process with an interstitial tissue reaction, whereas glomerular alterations are of a secondary character. Tubulointerstitial lesions can thus account for the symptoms of the disease, i.e. tubular proteinuria and reduced urine concentration capacity and urine acidification. Also, an increased incidence of malignant tumours of the urinary tract was found in the same geographic area.

Epidemiology of Balkan endemic nephropathy.

The first outbreak of Balkan endemic nephropathy (BEN) was reported between 1955 and 1957, initially in Serbia and soon afterwards in Croatia and in Bosnia and Herzegovina. The disease appears to be of a focal nature. In Yugoslavia at least six foci are known, generally along major rivers of the Danubian river basin, in areas that have often been flooded in the past and even today suffer from high ground waters. The prevalence rate of the disease is reported to be between 2 and 10%. In the endemic area of Croatia, a systematic survey of 'in-the-field' cases of the disease since 1975 has shown a prevalence between 0.5 and 4.4%. When suspected cases are also included the prevalence rises to 20% or more. Specific mortality (based on official statistics) during the period 1957-1984 averaged 1.54/1000 per annum, but some studies have shown that mortality is actually more than twice as high as this figure. More women are affected than men; women also more frequently die of BEN than men. Lethality is extremely high. A striking feature of BEN is the familial occurrence of the disease. Incidence does not seem to be connected with ethnic group differences. Immigrants into the endemic area may also contract the disease. An increased incidence of malignant tumours of the urinary tract has been recorded in populations living in endemic areas. Epidemiological characteristics suggest that the disease is contracted in the domestic situation, or possibly from other family members. Factors to be considered are food, water or long close contact. It is also possible that the disease is contracted outside the house, in connection with farming activities, since the affected persons are almost exclusively farmers.

Beta 2-microglobulin studies in endemic Balkan nephropathy.

The diagnosis of BEN and its differentiation from other chronic interstitial nephropathies are difficult because of the insidious onset as well as nonspecific morphological changes in the kidney. Early diagnosis of this disease is by clinical and laboratory findings which have not been universally accepted. This study was designed to determine if the frequency of increased urinary beta 2-microglobulin (U beta 2m) in village populations at risk to develop BEN was significantly higher than that seen in a control population. Individuals in the two population samples were classified in one of three categories: healthy, suspect or diseased. There were 23 individuals who met the criteria for the clinical diagnosis of BEN. Twenty (87%) of these had one or more positive tests for increased U beta 2m. The prevalence of kidney disease in the endemic village population sample was 13.4 times that for the control village population sample. The data show that the healthy individuals living in a village where BEN is endemic have 6.4 times greater chance of having tubular proteinuria than those living in a control area. The coincidence of the finding of U beta 2m in the urine of 87% of those sick with BEN and in 37 of the 342 (10.8%) people judged to be free of kidney disease suggests that a positive U beta 2m test is an early indicator of exposure to a nephrotoxic agent.

A fifteen year cohort based evaluation of beta 2-microglobulin as an early sign of Balkan endemic nephropathy.

The occurrence of elevated urinary beta 2-microglobulin (U beta 2m) has been established to be more common in village populations living in areas where BEN is endemic when compared to appropriate control population. In addition, beta 2-microglobulinuria is associated with BEN. It has been demonstrated that there is an increase in the U beta 2m in apparently healthy populations located in high risk areas. It is 15 years since the first systematic investigations of U beta 2m in the villages of Brod Posavina were conducted. The purpose of this study was to determine the value of a positive test for tubular proteinuria as defined by increased U beta 2m, in identifying individuals at risk to develop BEN. In these studies we followed two cohorts for 15 years: one group consisted of individuals who were positive for tubular proteinuria by U beta 2m testing in 1974; the second group was an age and sex matched group from the same village who were never positive after 12 testings in 1974. The results show that a positive test for U beta 2m is associated with 9.9 times greater relative risk of developing BEN when compared to controls that had no positive U beta 2m tests.

Relationship of anemia to Balkan endemic nephropathy.

Anemia has been reported to be an early sign of Balkan endemic nephropathy (BEN) occurring before the serum creatinine is elevated. This study was designed to determine if anemia occurred more frequently in an otherwise 'healthy' population living in an area where BEN is endemic when compared to a control population. Also, we wished to determine if any relationship existed between anemia and beta 2-microglobulinuria (beta 2mu) in these populations. The prevalence of anemia in the control village population was 7%, compared to 21.4% of the at-risk village population. These data suggest that anemia is a part of the pathophysiologic picture of endemic nephropathy, and that anemia can be found in an early, non-azotemic phase of the kidney disease.

Human exposure to ochratoxin A.

Over a nine-year period during screening campaigns in villages where Balkan nephropathy is endemic, human blood samples were collected and analysed for ochratoxin A. The incidence of positive samples was 0.5-2.5%. Dried beans were found to be more frequently contaminated with the toxin than other food commodities. In view of a specific accumulation of ochratoxin A observed in eggs, more attention should be paid to contamination of this food with ochratoxin A.

Haematological features of the population of the area of Croatia, Yugoslavia, endemic for Balkan nephropathy.

Normochromic, normocytic anaemia is a sign recognized as essential for the diagnosis of Balkan endemic nephropathy, although its relationship to the disease is still unclear. The aim of this study was to investigate whether a random sample of the population of a village endemic for nephropathy differed from the population of a village with no clinical case of nephropathy with respect to certain basic haematological parameters. During a screening campaign in 1984, 133 blood samples were collected from the endemic village and 40 from the nonendemic village and analysed for a number of haematological parameters; in 1991, 449 samples were collected in the endemic village and 156 in the nonendemic village and analysed for haemoglobin content and red blood cell count. Whereas in 1984 the haemoglobin content and red blood cell count were significantly lower in the endemic village (p less than 0.01), in 1991 the erythrocyte count was much lower in the nonendemic village and there was no difference in haemoglobin concentration. Several controversial explanations, all of them speculative, are offered.

Epidemiological aspects of Balkan endemic nephropathy in a typical focus in Yugoslavia.

Balkan endemic nephropathy is a noninflammatory bilateral kidney lesion that affects rural populations in several circumscribed areas of the Balkans. Its etiology is still not understood, but recently it has been associated with exposure to nephrotoxic mycotoxins. It has been known to be present since the mid-1950s in 14 villages in an endemic area of Croatia, where approximately 10,000 people are at risk. Its prevalence fluctuates between 0.4 and 8.3%, showing a slight decline in recent years, but it has not disappeared from any of the endemic villages. The occurrence of the disease in several ethnic groups contradicts the hypothesis of a primary hereditary basis for Balkan endemic nephropathy. Recently, evidence has been found of an extremely high incidence of urinary tract tumours in the endemic area, and particularly of urothelial tumours of the pelvis and ureter. There may therefore be a common causative agent for these two rare diseases.

Human exposure to ochratoxin A in areas of Yugoslavia with endemic nephropathy.

Ochratoxin A is a mycotoxin with pronounced nephrotoxic potency in all species of single-stomach animals studied; it is a major disease determinant of porcine nephropathy and a disease occurring endemically in several countries. This disease is comparable with Balkan (endemic) nephropathy, suggesting a common causal relationship. Ochratoxin A has been found in foodstuffs in many countries, but the highest frequency of ochratoxin A contamination in foods (10.3% of 1,553 samples of foodstuffs) was encountered in an area of Yugoslavia, where Balkan (endemic) nephropathy is prevalent. Detection of ochratoxin A in human blood samples confirmed the prevalent exposure to this food contaminant. Relative risk calculations indicated a tendency to an association between this mycotoxin and Balkan (endemic) nephropathy, supporting the hypothesis of a causal role of ochratoxin A in this disease.

Tamm-Horsfall protein determination in Balkan endemic nephropathy.

Data on the excretion of Tamm-Horsfall protein (THP) in subjects living in an area of Balkan endemic nephropathy (BEN) are reported. The study subjects were divided into groups as follows: diseased, suspect, "at risk" and others, according to previously adopted criteria. The THP excretion in "at risk" subjects was found to be significantly higher as compared to control subjects. The difference between these two groups could not be registered by any other clinical or laboratory diagnostic methods. No difference in the excretion of THP was observed between the groups of others and control subjects. According to the results obtained, the excretion of THP may be considered a possibly useful additional diagnostic test for the detection of subjects with the latent, early subclinical phase of BEN. On the other hand, the data obtained shed some more light on the still obscure pathogenesis and natural history of BEN.

An etiological approach to Balkan endemic nephropathy based on the investigation of two genetically different populations.

The direct inheritance as a possible etiologic factor of Balkan endemic nephropathy (BEN) has been studied in an endemic area in the district of Slavonski Brod (Croatia-Yugoslavia). The basis for the investigation was given by a natural experiment induced by immigration of people from Ukraina to the endemic and nonendemic areas near Slavonski Brod. 1,536 persons in endemic villages and 733 inhabitants from the villages, where BEN has not been found, were studied with the aim of establishing diagnosis or excluding BEN. The generally adopted criteria enabling to classify the examined persons into the following 3 groups have been used: (a) diseased of BEN; (b) suspect to be diseased of BEN, and (c) individuals without signs of a renal disease. In the endemic villages among the population of Croatian aborigines, 12,1% diseased and suspects have been revealed. Among the Ukrainian immigrants and their offsprings, 10.5% diseased and suspects have been found. The difference is not significant (t = 0.7, p greater than 0.05). On the other hand, in nonendemic villages there were no diseased nor suspect BEN patients among the indigenous people as well as among the Ukrainians. The inference is suggested that the factors of the direct inheritance do not play a decisive role in the etiopathogenesis of BEN.

Screening for ochratoxin A in blood by flow injection analysis.

A micromethod for ochratoxin A detection in human sera by flow injection technique is described. The method requires 50 microliter of sera, and it is designed to distinguish samples containing less than 10 ng ochratoxin A per ml. The method is based on fluorescence measurement following a simple extraction procedure for which very small amounts of chemicals are needed. Since the method is not confirmatory, all samples showing fluorescence above a certain intensity have to be reanalysed with some other method where a confirmation step in included. Because of the small amount of serum needed and the rapid procedure (less than 15 min), a large number of samples can be analysed very quickly. The method may therefore be applicable for large screening campaigns conducted to determine the presence of ochratoxin A in blood. This conclusion is based on 1675 samples and 147 standards analysed concurrently by the flow injection technique and an earlier published enzymic method. The method is also suitable for monitoring ochratoxin A levels in the blood of experimental animals.

Characteristics of proteinuria in endemic nephropathy.

Subjects living in the endemic area of Posavina round Slavonski Brod have a significantly greater incidence of proteinuria (13.6%) than those living under the same conditions in the area where endemic nephropathy has not been observed (5.5%). Following determination of the grade and type of proteinuria, physiologic proteinuria was found in 36% of subjects from the endemic area. In nonphysiologic proteinuria the incidence of tubular proteinuria was 41%. A slight selective glomerular proteinuria was found in 51%, and other types of proteinuria in 8% of subjects. Tubular proteinuria was significantly higher in the endemic area than in the control area. The subjects with tubular proteinuria from the endemic area excrete significantly greater amounts of beta 2-microglobulin and light immunoglobulin chains.

Balkan (endemic) nephropathy and foodborn ochratoxin A: preliminary results of a survey of foodstuffs.

Ochratoxin A is a nephrotoxic fungal metabolite (mycotoxin) occurring in foodstuffs. The compound is causally associated with mycotoxic porcine nephropathy, a disease comparable with a human kidney disease, Balkan endemic nephropathy. A preliminary survey of home-produced foodstuffs in areas of Yugoslavia revealed that contamination with ochratoxin A is more frequent in an area where Balkan endemic nephropathy is prevalent (endemic area) than in area where this disease is absent. This indicates higher exposure to foodborn ochratoxin A in the endemic area. Thus further evidence is provided supporting the hypothesis that ochratoxin A is a disease determinant of Balkan endemic nephropathyk0