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Published on: October 21, 2018
Change in Measured GFR Versus eGFR and CKD Outcomes
Elaine Ku1, Dawei Xie2, Michael Shlipak3
1Division of Nephrology, Department of Medicine, Division of Pediatric Nephrology, Department of Pediatrics, and elaine.ku@ucsf.edu.
Abstract:
Measured GFR (mGFR) has long been considered the gold standard measure of kidney function, but recent studies have shown that mGFR is not consistently superior to eGFR in explaining CKD-related comorbidities. The associations between longitudinal changes in mGFR versus eGFR and adverse outcomes have not been examined. We analyzed a subset of 942 participants with CKD in the Chronic Renal Insufficiency Cohort Study who had at least two mGFRs and two eGFRs determined concurrently by iothalamate and creatinine (eGFRcr) or cystatin C, respectively. We compared the associations between longitudinal changes in each measure of kidney function over 2 years and risks of ESRD, nonfatal cardiovascular events, and all-cause mortality using univariate Cox proportional hazards models. The associations for all outcomes except all-cause mortality associated most strongly with longitudinal decline in eGFRcr. Every 5-ml/min per 1.73 m(2) decline in eGFRcr over 2 years associated with 1.54 (95% confidence interval, 1.44 to 1.66; P<0.001) times higher risk of ESRD and 1.23 (95% confidence interval, 1.12 to 1.34; P<0.001) times higher risk for cardiovascular events. All-cause mortality did not associate with longitudinal decline in mGFR or eGFR. When analyzed by tertiles of renal function decline, mGFR did not outperform eGFRcr in the association with any outcome. In conclusion, compared with declines in eGFR, declines in mGFR over a 2-year period, analyzed either as a continuous variable or in tertiles, did not consistently show enhanced association with risk of ESRD, cardiovascular events, or death.
Insights
Longitudinal decline in estimated glomerular filtration rate (eGFR) better predicts adverse kidney outcomes than measured glomerular filtration rate (mGFR). Declines in both eGFR and mGFR did not associate with all-cause mortality risk.
Area of Science:
- Nephrology
- Renal Function Assessment
- Chronic Kidney Disease (CKD) Research
Background:
- Measured glomerular filtration rate (mGFR) is the gold standard for kidney function assessment.
- Recent evidence questions mGFR's consistent superiority over estimated glomerular filtration rate (eGFR) in explaining CKD comorbidities.
- Longitudinal changes in mGFR versus eGFR and their association with adverse outcomes remain underexplored.
Purpose of the Study:
- To compare the associations between longitudinal changes in mGFR and eGFR with adverse outcomes in CKD patients.
- To determine if mGFR offers superior predictive value over eGFR for end-stage renal disease (ESRD), cardiovascular events, and mortality.
Main Methods:
- Analysis of a subset of 942 CKD participants from the Chronic Renal Insufficiency Cohort Study.
- Inclusion of participants with at least two concurrent mGFR (iothalamate) and eGFR (creatinine-based [eGFRcr] or cystatin C-based) measurements over 2 years.
- Univariate Cox proportional hazards models were used to compare associations between kidney function decline and risks of ESRD, nonfatal cardiovascular events, and all-cause mortality.
Main Results:
- Longitudinal decline in eGFRcr showed the strongest association with ESRD and cardiovascular events.
- A 5-ml/min/1.73 m² decline in eGFRcr over 2 years was linked to a 1.54-fold higher risk of ESRD and a 1.23-fold higher risk of cardiovascular events.
- Neither mGFR nor eGFR longitudinal decline consistently associated with all-cause mortality, and mGFR did not outperform eGFRcr in predicting any outcome.
Conclusions:
- Longitudinal declines in eGFR, particularly eGFRcr, are more strongly associated with ESRD and cardiovascular events than mGFR declines.
- mGFR did not demonstrate superior predictive ability compared to eGFRcr for adverse outcomes when analyzed continuously or by tertiles.
- Current findings suggest eGFR changes may be more informative than mGFR changes for risk stratification in CKD patients.
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