title: Challenges for the present CKD classification system.
abstract: OBJECTIVE
  In 2002 the Kidney Disease Outcomes Quality Initiative (K/DOQI) organization published a guideline on chronic kidney disease (CKD), which contained a classification system for CKD severity, independent of cause. This classification system was immediately widely embraced. However, soon after its introduction concerns were expressed. In this review we discuss the major points of concern that have been brought forward.
  
  
  RESULTS
  Although the reliability of the Modification of Diet in Renal Disease study estimation equation for glomerular filtration rate (GFR) is disputed, it is useful for the vast majority of individuals. In cases of abnormal muscular build, however, other GFR estimations should be used. Cystatin C-based equations are promising in that respect. On the basis of recent literature we propose that the present CKD classification scheme should be adapted insofar that stage 3 CKD should be split into two, and that information on albuminuria should be added to all CKD classes. Individuals with an estimated GFR between 45 and 60 ml/min/1.73 m2 and without microalbuminuria or macroalbuminuria are in general not at risk for renal or cardiovascular disease progression and should not be labelled as having CKD. In our opinion there is no strong rationale to introduce age-specific cut-off values indicating CKD.
  
  
  CONCLUSIONS
  These recent epidemiological findings will hopefully form a basis for an adaptation of the present CKD classification system that will meet broad acceptance again.
authors.affiliation: Department of Nephrology, University Medical Center Groningen, Groningen, The Netherlands. R.T.Gansevoort@int.umcg.nl
authors.forename: Ron T
authors.initials: RT
authors.lastname: Gansevoort
authors.forename: Paul E
authors.initials: PE
authors.lastname: de Jong
mesh_terms: D006801:Humans; D007676:Kidney Failure, Chronic / Q000145:classification*