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The third cause of admission to dialysis in Argentina is not filiated, Diabets and Hypertension are the first and second cause respectevily. To date, there is no study of the population of patients who enter dialysis with CKD of unknown cause (CKDUO) in Argentina. Our aim wasto describe the patients who enter dialysis in Argentina with CKDUO, estimate the survival of this subgroup of patients and compare it with the rest of the population that enters dialysis. Describe the number of kidney biopsies performed in incident dialysis patients, and explore their association with socioeconomic and social health indicators.
Observational, retrospective cohort study with data obtained from the National Dialysis and Transplant Registry. In Argentina, it is mandatory the registration of incident patients on chronic renal replacement therapy and organ transplantation. This registration contains identification data, laboratory analyses, type of vascular access and patient´s comorbidities as well as the cause of ending renal replacement therapy (death). These variables are registered in an online form called DRI, which ensures data availability from all the country. Patients who were admitted to chronic hemodialysis for the first time in their lives in all Hemodialysis Centers of the Argentine Republic between April 1, 2004 and December 31, 2015 were included. The population was classified into 2 groups according to registry data: 1) CKDUO, 2) CKD with known diagnosis. The outcome variable “death” was considered in the survival analysis, as time to occurrence of the event. Kaplan Meier curves were constructed and the difference between them was evaluated using the log-rank test. Survival was adjusted for age, sex and presence of diabetes. Values of p < 0.05 were considered significant.
Total 116066 incident dialysis patients were included, with the CKDUO cohort of 19858 patients (17.1%) . These patients had a lower average age (62.5% verus 57% under 65 years old), higher prevalence of females (42.2% versus 41%), a higher prevalence of foreigners (6.7% vs. 5.3%), greater public health financing (24.5% vs. 20.7%), and worse housing conditions. Higher use of a temporary vascular access for admission to dialysis (69 vs. 65%). Upon admission, the patients in the cohort had a higher creatinine (8.3 mg/dl vs. 7 mg/dl) and a significantly lower glomerular filtration rate than the rest of the patients. The survival of the CKDUO patients was higher, with an average of 43.7 months (95% CI 42.1 to 44.8) versus 34.5 months (95% CI;34.2 to 34.9) for the rest of the patients. The Hazard Ratio (HR) of mortality for the Unknown Etiology group was 0.97 (95% CI; 0,9454- ,9904), p<0.01. The national average proportion of biopsied patients is only 9.4%, with heterogeneity between provinces (4.4 to 15%), which was significantly correlated with the percentage of urban population (direct correlation) and with the percentage of unmet basic needs (inverse correlation).
Patients with CKDUO are younger, with a more precarious socio-economic situation and with indicators of late or absent attention regarding renal health care. Kidney biopsy, a fundamental diagnostic tool, showed correlation with the socio-health indicators. Health actions and policies are required that allow accessibility to kidney health in earlier instances of chronic kidney disease.