In 2002 at the Spring Clinical Meeting of the National Kidney Foundation, K/DOQI released the Clinical Practice Guidelines for Chronic Kidney Disease Evaluation, Classification and Stratification.
These guidelines have become the dogma of CKD and all of my residents can accurately determine the CKD stage of their patients. The classifications have allowed epidemiologists to measure the burden of CKD. The crux of the guideline is that the severity of kidney disease is solely determined by the GFR. This is helpful in determining where the patient has been but it is not good at determining where patients are headed.
In some ways, it is a negative prognostic tool, people with worse stages of CKD actually have better outcomes and vice versa.
To understand how this works one needs to understand how we calculate the GFR. The accepted equation was created by Levey et al using the MDRD data base. Levey AS, Greene T, Kusek JW, Beck GJ: A simplified equation to predict glomerular filtration rate from serum creatinine. J Am Soc Nephrol 11:A0828, 2000 (abstract)
GFR=186 x sCr -1.154 x Age -0.203 x (0.742 if female) x (1.212 African-American)
African Americans, for the same creatinine, are given a 21% increase in their GFR and women lose 26%. If GFR provided prognostic information one would think that African Americans were protected from chronic kidney disease and women were at higher risk. Yet that is not the case. African Americans have the highest rates of ESRD, 998 per million compared to 273 for white Americans: (USRDS 2009 Annual Data Reports, NIH, NIDDK, Bethesda, MD, 2009.)
