The Design and Conduct of Cohort Studies of Peoples With CKD - International Perspectives From iNET-CKD.

Prospective cohort studies are important for understanding epidemiology, associations, and incidence of adverse outcomes of long-term conditions, including chronic kidney disease (CKD). Here, we draw on the combined expertise of the leaders of cohort studies within the ISN's International Network of CKD Cohorts (iNET-CKD) to provide insights into the design and conduct of prospective cohort studies in people with CKD. Formulating research questions that will remain relevant years after the cohort launch, when data will be available, is the first, and perhaps most challenging step of the study design. These questions will inform participant selection, sample size, duration of follow-up, outcome definitions, as well as frequency of encounters and data collection. Consideration should be given to the data elements to be collected, balancing burden with data value. At least 1 marker of glomerular filtration rate (GFR) (preferably both serum creatinine and cystatin C concentrations) and a measure of proteinuria (preferably urine albumin-to-creatinine ratio) are essential. Standard operating procedures should be developed for all assessments and for biosample collection and storage. Robust governance arrangements should be established to ensure effective management and sustainability of these complex projects, along with sufficient funding for the proposed study duration. Facilitating future collaboration with other cohort studies should be born in mind, to expand scientific output. This includes adoption of standard definitions and assessments, as well as making provisions for sharing of data and biosamples. A clear communication strategy that includes all stakeholders is essential to ensure maximum clinical impact.