title: International Collaboration for the Epidemiology of eGFR in Low and Middle Income Populations - Rationale and core protocol for the Disadvantaged Populations eGFR Epidemiology Study (DEGREE).
abstract: There is an increasing recognition of epidemics of primarily tubular-interstitial chronic kidney disease (CKD) clustering in agricultural communities in low- and middle-income countries (LMICs). Although it is currently unclear whether there is a unified underlying aetiology, these conditions have been collectively termed CKD of undetermined cause (CKDu). CKDu is estimated to have led to the premature deaths of tens to hundreds of thousands of young men and women over the last 2 decades. Thus, there is an urgent need to understand the aetiology and pathophysiology of these condition (s). International comparisons have provided the first steps in understanding many chronic diseases, but such comparisons rely on the availability of standardised tools to estimate disease prevalence. This is a particular problem with CKD, since the disease is asymptomatic until the late stages, and the biases inherent in the methods used to estimate the glomerular filtration rate (GFR) in population studies are highly variable across populations.
  
  
  
  We therefore propose a simple standardised protocol to estimate the distribution of GFR in LMIC populations - The Disadvantaged Populations eGFR Epidemiology (DEGREE) Study. This involves the quantification of renal function in a representative adult population-based sample and a requirement for standardisation of serum creatinine measurements, along with storage of samples for future measurements of cystatin C and ascertainment of estimates of body composition, in order to obtain valid comparisons of estimated GFR (eGFR) within and between populations.
  
  
  
  The methodology we present is potentially applicable anywhere, but our particular focus is on disadvantaged populations in LMICs, since these appear to be most susceptible to CKDu. Although the protocol could also be used in specific groups (e.g. occupational groups, thought to be at excess risk of CKDu) the primary aim of the DEGREE project is characterise the population distribution of eGFR in multiple regions so that international comparisons can be performed. It is only with a standardised approach that it will be possible to estimate the scale of, and variation in, impaired kidney function between affected areas. These data should then provide insights into important social, demographic and environmental risk factors for this increasingly recognised disease.
authors.affiliation: Centre for Nephrology, UCL Medical School Royal Free, London, NW3 2PF, UK. b.caplin@ucl.ac.uk.
authors.forename: Ben
authors.identifier: 0000-0001-9544-164X
authors.initials: B
authors.lastname: Caplin
authors.affiliation: Division of Occupational and Environmental Medicine, Sahlgrenska Academy, Gothenburg University, Gothenburg, Sweden.|Division of Occupational and Environmental Medicine, Lund University, Lund, Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Jakobsson
authors.affiliation: La Isla Foundation, Ada, Michigan, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Glaser
authors.affiliation: Department of Non-Communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Dorothea
authors.initials: D
authors.lastname: Nitsch
authors.affiliation: George Institute for Global Health India, New Delhi, India.|University of Oxford, Oxford, UK.
authors.forename: Vivekanand
authors.initials: V
authors.lastname: Jha
authors.affiliation: Department of Global and Continuing Education, Harvard Medical School, Boston, USA.
authors.forename: Ajay
authors.initials: A
authors.lastname: Singh
authors.affiliation: Department of Nephrology and Mineral Metabolism at the Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubirán, Mexico City, Mexico.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Correa-Rotter
authors.affiliation: Department of Non-Communicable Disease Epidemiology and Centre for Global NCDs, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Neil
authors.initials: N
authors.lastname: Pearce
mesh_terms: D003404:Creatinine / Q000097:blood*; D003906:Developing Countries; D005919:Glomerular Filtration Rate; D006801:Humans; D013058:Mass Spectrometry; D011203:Poverty / Q000706:statistics & numerical data*; D015995:Prevalence; D051436:Renal Insufficiency, Chronic / Q000453:epidemiology* / Q000378:metabolism
chemical_list: D003404:Creatinine
keywords: Chronic kidney disease of undetermined cause; Chronic kidney disease prevalence; Estimated glomerular filtration rate; Low- and middle-income countries; Mesoamerican nephropathy