Epidemiology of chronic kidney disease: think (at least) twice!

The introduction of the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines has substantially contributed to the early detection of different stages of chronic kidney disease (CKD). Several recent studies from different parts of the world mention a CKD prevalence of between 8 and 13%. There are several reasons the CKD prevalence found in a study of a particular population is clearly overestimated. The structure of the population pyramid (young or older age) of the study sample may result in high or low CKD prevalence. The absence of using an isotope dilution mass spectrometry creatinine assay can be the source of high bias in CKD prevalence. In addition, using an arbitrary single threshold of estimated glomerular filtration rate (eGFR; <60 mL/min/1.73 m²) for classifying CKD leads to a substantial 'overdiagnosis' (false positives) in the elderly (>65 years of age), particularly in those without albuminuria (or proteinuria), haematuria or hypertension. It also results in a significant 'underdiagnosis' (false negatives) in younger individuals with an eGFR >60 mL/min/1.73 m² and below the third percentile for their age/gender category. The use of third percentile eGFR rates as a cut-off based on age/gender-specific reference values of eGFR allows the detection of these false positives and negatives. In the present article, we focus on an important and frequently omitted criterion in epidemiological studies: chronicity. Indeed, the two most important factors introducing a high number (up to 50%) of false positives are lack of confirming proteinuria and the absence of proof of chronicity of the eGFR found at first screening. There is an urgent need for quality studies of the prevalence of CKD using representative randomized samples of the population, applying the KDIGO guidelines correctly.