Study design and data source

This study is an observational cohort study, performed on the Renal Information Management System (iRIMS), which collects demographic and clinical data prospectively from all patients treated within a multi-national dialysis network. Routine laboratory parameters are collected monthly or at greater intervals for control of anemia, acid-base and electrolyte balance, nutrition, inflammation and chronic kidney disease (CKD)-mineral and bone disorder and dialysis efficacy.

For this study, laboratory data for the observational period between 3 March and 3 July 2020, and the three preceding months were retrieved. In addition, demographic and clinical data, dialysis-specific parameters and information about medications were obtained. Patients with a COVID-19 diagnosis were identified through an incidence reporting system, which is part of the iRIMS registry. A COVID-19 diagnosis was defined by a positive SARS-CoV-2 PCR sample.Severe COVID-19 was defined as a diagnosis of COVID-19 in combination with hospital admission or death. Primary outcome for this study was the incidence of COVID-19. Secondary outcomes were incidence of severe disease and death due to COVID-19. Any death or hospitalization that occurred during the observational period after diagnosis of COVID-19 was registered and considered to be associated with COVID-19. Causes of death are routinely registered in the iRIMS database by dialysis personnel at each dialysis facility, based on hospital records. The categories available in iRIMS are cardiac, cerebral, infection, liver disease, gastro-intestinal bleeding, metabolic, endocrinologic and other. Categorization is performed by health care personnel and treating physician at each dialysis facility. The study was performed in accordance with the Declaration of Helsinki and its amendments. All patients have given informed consent to collection of data in iRIMS. For the current registry study, data were extracted anonymously, therefore, no separate informed consent was required.