The global burden of chronic kidney disease: estimates, variability and pitfalls.

Chronic kidney disease (CKD) is currently defined by abnormalities of kidney structure or function assessed using a matrix of variables - including glomerular filtration rate (GFR), thresholds of albuminuria and duration of injury - and is considered by many to be a common disorder globally. However, estimates of CKD prevalence vary widely, both within and between countries. The reasons for these variations are manifold, and include true regional differences in CKD prevalence, vagaries of using estimated GFR (eGFR) for identifying CKD, issues relating to the use of set GFR thresholds to define CKD in elderly populations, and concerns regarding the use of one-off testing for assessment of eGFR or albuminuria to define the prevalence of CKD in large-scale epidemiological studies. Although CKD is common, the suggestion that its prevalence is increasing in many countries might not be correct. Here, we discuss the possible origins of differences in estimates of CKD prevalence, and present possible solutions for tackling the factors responsible for the reported variations in GFR measurements. The strategies we discuss include approaches to improve testing methodologies for more accurate assessment of GFR, to improve awareness of factors that can alter GFR readouts, and to more accurately stage CKD in certain populations, including the elderly.