The Case for Using Albuminuria in Staging Chronic Kidney Disease

The publication of the Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines for the evaluation, classification, and stratification of chronic kidney disease (CKD) in 20021 has greatly raised awareness of CKD and stimulated epidemiologic research investigating the consequences of CKD. Its publication and distribution were also followed by critical commentaries. The authors of these commentaries questioned whether it is correct to claim someone has chronic disease without having firm evidence that that chronic disease will lead to a worse prognosis.2,3 They suggested that the CKD staging system be changed—one change among others—by not paying attention to stages 1 and 2 CKD, which are characterized by early signs of renal damage (albuminuria, erythrocyturia, or abnormalities on ultrasonography) and normal or near-normal estimated GFR (eGFR). Critical authors argued that this modification would make the staging system more simple and useful.2,3 In this commentary, we suggest that the discounting of stages 1 and 2 CKD is not justified on the basis of recent evidence from various epidemiologic studies and indicate further that there is need to examine more carefully the clinical prognosis of individuals with stage 3 CKD. The main value of a CKD classification system is in providing insight regarding risk for developing ESRD. That renal function often declines gradually makes it more likely that a patient who ends with ESRD will have previously gone through the five levels of severity of CKD; that is, from a normal GFR of >90 ml/min down to a GFR of <15 ml/min. It is unreasonable to assume, however, that all patients with the earlier stages of CKD will likely progress to ESRD. Stages 1 through 3 CKD are present in ≥10% of the population,4–6 whereas each year going forward fewer than one of the 1000 of …