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The advantage of a uniform terminology and staging system for chronic kidney disease (CKD)

2003; Oxford University Press; Volume: 18; Issue: 8 Linguagem: Inglês

10.1093/ndt/gfg241

1460-2385

Adeera Levin,

Renal Diseases and Glomerulopathies

Chronic kidney disease is an epidemic facing most western countries, with annual dialysis growth rates 6–8% per annum. There is an increasing awareness of the immense size of the patient group with kidney disease who do not require dialysis, as derived from analysis of population databases [1]. In a recent publication, the National Kidney Foundation sponsored Kidney Disease Outcomes Quality Initiative (KDOQI) working group proposed a set of guidelines regarding the definition, classification and evaluation of chronic kidney disease [2]. Using large representative databases of both referred and non-referred patients, and evidence-based examination of the literature, five stages of kidney disease have been defined. These stages correspond to the severity of kidney function loss and the prevalence of co-morbidities associated with kidney disease. Importantly, the classification system describes the stages according to level of estimated glomerular filtration rate (GFR), not serum creatinine levels, and advocates for the use of estimated GFR values to be used in evaluation of all patients. The new classification system does not suggest that all persons with kidney disease will require dialysis, nor that they will all progress through each stage; instead, the evidence reviewed suggests that patients with sustained lowGFR are at increased risk for acute deterioration in function, and will have higher health resource utilization and death rates than the general population. A recent set of international studies [3–5] and previous publications have demonstrated that there continues to be late referral to nephrologists by both primary care physicians and specialists, and that the majority of patients are referred with advanced kidney disease, often at average GFR levels of 30 ml/min/1.73m (stage 3/4 CKD) [6–8]. Given the accumulating data regarding the increasing prevalence of risk factors for cardiovascular and progressive kidney disease at lower levels of GFR, current referral practices preclude the nephrology community’s attempt to prevent or delay progression of disease. Furthermore, and perhaps even more unsettling, is the finding that despite numerous guidelines to screen patients at high risk for CKD (diabetics and those with hypertension of cardiovascular disease) many patients remain unscreened or poorly characterized with respect to the extent of kidney disease [5,9,10]. There are numerous consequences of kidney disease prior to dialysis including hypertension, anaemia, cardiovascular disease, mineral metabolism abnormalities and nutritional impairment [11–14]. Strategies for prevention of these consequences, which are associated with a high burden of illness and resource utilization, include public and professional education, policy change and influence, and an increased research effort (basic, clinical and outcome based) [15,16]. Numerous barriers exist to implementation of intervention strategies, which include (i) continued late referral, (ii) paucity of data for some interventional strategies at all levels of kidney function, (iii) problems with measurement of the marker/screening tool for kidney function (serum creatinine) and (iv) unawareness of the problem due to confusing communication with patients, physicians and policy makers. The inaccuracy of serum creatinine as a marker for kidney disease, and the confusing terminologies and approaches to kidney disease have undoubtedly contributed to the late referral, which in turn has contributed to the lack of large clinical trials in early kidney disease populations. The purpose of this paper is to describe the advantages and rationale for a common terminology of CKD and its stages, as proposed by the NKF Working group in AJKD, February 2002 [2]. Many in the nephrology communitymaywonder if such a system is necessary, and have chosen to question the specific guidelines regarding estimation of GFR, and thus challenge the essence of the classification system [17–19]. This article attempts to contextualize the discussionwithin the current era of increasing awareness of kidney disease, describes the importance of the proposed system, the value of adopting objective and clear definitions, and the advantages of this approach. However, it also recognizes that there are limitations to any classification system. These limitations should be viewed as appropriate for research and refinement Correspondence and offprint requests: A. Levin MD FRCPC, St Paul’s Hospital, 1081 Burrard Street, Room 6010A, Vancouver BC V6Z 1Y8, Canada. Email: alevin@providencehealth.bc.ca