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Comparison of concurrent complications of CKD by 2 risk categorization systems
Lesley A Inker1, Marcello Tonelli, Brenda R Hemmelgarn
1Tufts Medical Center, Boston, MA 02111, USA. linker@tuftsmedicalcenter.org
Insights
The NKF-KDOQI system, primarily using estimated glomerular filtration rate (eGFR), may better identify chronic kidney disease (CKD) complications than systems incorporating proteinuria. This impacts CKD staging and patient evaluation.
Area of Science:
- Nephrology
- Public Health
- Clinical Epidemiology
Background:
- Classifying chronic kidney disease (CKD) severity using both estimated glomerular filtration rate (eGFR) and proteinuria is proposed.
- The clinical utility of such a combined staging system for evaluating CKD complications remains unclear.
Purpose of the Study:
- To compare the effectiveness of two CKD classification systems in identifying concurrent complications.
- To evaluate a staging system using both eGFR and proteinuria against the NKF-KDOQI system (primarily eGFR).
Main Methods:
- Cross-sectional analysis of 30,528 participants from the US National Health and Nutrition Examination Survey (1988-2006).
- GFR estimated using CKD-EPI equation; proteinuria assessed via urine albumin-creatinine ratio.
- Compared NKF-KDOQI system with an alternative system incorporating proteinuria for CKD staging.
Main Results:
- The NKF-KDOQI system showed increasing prevalences of anemia, acidosis, hyperphosphatemia, hypoalbuminemia, hyperparathyroidism, and hypertension with CKD severity.
- The alternative system (eGFR + proteinuria) showed lower prevalences of some complications in stage 3 compared to stage 2.
- While the alternative system better reclassified participants without complications, it inappropriately reclassified those with complications to lower stages.
Conclusions:
- The NKF-KDOQI staging system may be superior in identifying specific concurrent CKD complications.
- Systems incorporating both eGFR and proteinuria may lead to inappropriate downstaging of patients with complications.
Background:
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 the evaluation of concurrent CKD complications is not known.
Study Design:
Cross-sectional analysis.
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).
Predictors:
Classification system that uses both eGFR and proteinuria (alternative) and a system that primarily uses eGFR (NKF-KDOQI [National Kidney Foundation's Kidney Disease Outcomes Quality Initiative]).
Outcomes:
Prevalence of anemia, acidosis, hyperphosphatemia, hypoalbuminemia, hyperparathyroidism, and hypertension.
Measurements:
GFR estimated from the CKD Epidemiology Collaboration (CKD-EPI) equation and proteinuria assessed using urine albumin-creatinine ratio.
Results:
Prevalences 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, prevalences of anemia, acidosis, and hyperphosphatemia increased progressively from stage 2 through 4. With the alternative system, prevalences of anemia, hyperphosphatemia, hypertension, and hyperparathyroidism were lower in stage 3 than in 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 reclassified appropriately to lower stages (eg, overall net reclassification index of -6.5% for hyperparathyroidism). However, participants with complications (except for hypoalbuminemia) were more likely to be reclassified inappropriately to lower stages.
Limitations:
Use of a single creatinine measurement to estimate GFR and single measurement to assess albumin-creatinine ratio. Small number of participants with CKD stage 4.
Conclusions:
The NKF-KDOQI system may better identify patients with certain concurrent CKD complications compared with systems using eGFR and proteinuria.
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