Using both estimated glomerular filtration rate (eGFR) and proteinuria to classify the severity of chronic kidney disease (CKD) has been proposed. The utility of a staging system incorporating both eGFR and proteinuria for guiding evaluation of concurrent CKD complications is not known.
Setting & participants
30,528 participants in the US National Health and Nutrition Examination Survey conducted in 1988–1994 and 1999–2006 (n=8,242 for hyperparathyroidism).
Classification system that uses both eGFR and proteinuria (alternative) and a system that primarily uses eGFR (NKF-KDOQI; the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative)
Prevalence of anemia, acidosis, hyperphosphatemia, hypoalbuminemia, hyperparathyroidism and hypertension
GFR estimated from the CKD-Epidemiology Collaboration (CKD-EPI) equation and proteinuria assessed using urine albumin-creatinine ratio (ACR)
The prevalence of hypoalbuminemia, hypertension and hyperparathyroidism increased with more severe CKD using the NKF-KDOQI system. For example, the prevalence of hyperparathyroidism was 9.1%, 11.1%, 28.2% and 72.5% for Stages 1, 2, 3 and 4, respectively. Similarly the prevalence of anemia, acidosis and hyperphosphatemia increased progressively from Stage 2 through 4. With the alternative system, the prevalence of anemia, hyperphosphatemia, hypertension and hyperparathyroidism was lower in Stage 3 compared to Stage 2. For example, the prevalence of hyperparathyroidism was 13.5%, 40.3%, 22.2%, and 63.4% for stages 1, 2, 3 and 4, respectively. Applying the alternative system, participants without each complication were more likely to be appropriately reclassified to lower stages (for example, overall net reclassification index of −6.5% for hyperparathyroidism). However, participants with complications (except for hypoalbuminemia) were more likely to be inappropriately reclassified to lower stages.
Use of single creatinine to estimate GFR and single measure to assess ACR. Small number of participants with CKD Stage 4.
The NKF-KDOQI system may better identify patients with certain concurrent CKD complications compared to systems using eGFR and proteinuria.