The Biobank of Nephrological Diseases in the Netherlands cohort: the String of Pearls Initiative collaboration on chronic kidney disease in the university medical centers in the Netherlands.

Despite advances in preventive therapy, prognosis in chronic kidney disease (CKD) is still grim. Clinical cohorts of CKD patients provide a strategic resource to identify factors that drive progression in the context of clinical care and to provide a basis for improvement of outcome. The combination with biobanking, moreover, provides a resource for fundamental and translational studies. In 2007, the Dutch government initiated and funded the String of Pearls Initiative (PSI), a strategic effort to establish infrastructure for disease-based biobanking in the University Medical Centres (UMCs) in the Netherlands, in a 4-year start-up period. CKD was among the conditions selected for biobanking, and this resulted in the establishment of the Biobank of Nephrological Diseases-NL (BIND-NL) cohort. Patients with CKD Stages 1-4 are eligible. The data architecture is designed to reflect routine care, with specific issues added for enrichment, e.g. questionnaires. Thus, the collected clinical and biochemical data are those required by prevailing guidelines for routine nephrology care, with a minimal dataset for all patients, and diagnosis-specific data for the diagnostic categories of primary and secondary glomerular disorders and adult dominant polycystic kidney disease, respectively. The dataset is supplemented by a biobank, containing serum, plasma, urine and DNA. The cohort will be longitudinally monitored, with yearly follow-up for clinical outcome. Future linking of the data to those from the national registries for renal replacement therapy is foreseen to follow the patients' lifeline throughout the different phases of renal disease and different treatment modalities. In the design of the data architecture, care was taken to ensure future exchangeability of data with other CKD cohorts by applying the data harmonization format of the Renal DataSHaPER, with a dataset based upon standardized indicator sets to facilitate collaboration with other CKD cohorts. Enrolment started in 2010, and over 2200 eligible patients have been enrolled in the different UMCs. Follow-up of enrolled patients has started, and enrolment will continue at a slower rate. The aggregation and standardization of clinical data and biosamples from large numbers of CKD patients will be a strategic resource not only for clinical and translational research, but also by its basis in routine clinical care for clinical governance and quality improvement projects.

Different melatonin rhythms and sleep-wake rhythms in patients on peritoneal dialysis, daytime hemodialysis and nocturnal hemodialysis.

BACKGROUND: Little comparative data on sleep-wake rhythms in different dialysis groups exist. The aim of this study was to investigate sleep-wake parameters measured with actigraphy and sleep questionnaires as well as melatonin rhythms in automated peritoneal dialysis, conventional daytime hemodialysis and nocturnal hemodialysis patients. METHODS: Conventional daytime dialysis (n=20), nocturnal hemodialysis (n=13) and automated peritoneal dialysis patients (n=6) were included in the study. Melatonin in saliva was sampled at 5 time points (21:00, 23:00, 1:00, 7:00 and 9:00 h). Furthermore, actigraphy measurements and sleep questionnaires were performed. All parameters were tested by Kruskall-Wallis test (followed by post hoc Dunn test) to find significant differences (p<0.05). RESULTS: Although most sleep parameters were impaired in all three groups, conventional daytime dialysis patients had the worst sleep. In nocturnal hemodialysis patients a normal nocturnal melatonin rise was found. In daytime hemodialysis and automated peritoneal dialysis patients this rise was absent. CONCLUSIONS: The study showed impaired sleep parameters in all dialysis patient groups. As automated peritoneal dialysis is also performed during night time, the same effect on normalized melatonin was anticipated as was found in nocturnal hemodialysis. Melatonin seems to play a subordinate role in the sleep-wake rhythm of automated peritoneal dialysis patients.