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Comparison of Cystatin C-Based and Serum Creatinine-Based Renal Function Estimates Against Timed Urine Collection in
Sung Jin Jeong1, Andrew J Webb1, Kristy M Phillips2
1Massachusetts General Hospital, Boston, MA, USA.
Insights
The cystatin C-based eGFRcr-cys calculation showed less bias than the Cockcroft-Gault equation for estimating renal function in critically ill patients. Further research is needed to understand its clinical implications.
Area of Science:
- Nephrology
- Critical Care Medicine
- Clinical Chemistry
Background:
- Creatinine-based equations for estimating renal function, like Cockcroft-Gault (CG-CrCL), can be inaccurate in critically ill patients.
- Accurate renal function assessment is crucial for medication dosing and patient management in intensive care units (ICUs).
Purpose of the Study:
- To compare the accuracy of a cystatin C-based estimated glomerular filtration rate (eGFRcr-cys) calculation against measured creatinine clearance (mCrCL).
- To evaluate if eGFRcr-cys offers improved renal function estimation compared to CG-CrCL in critically ill adult patients.
Main Methods:
- A retrospective cohort study included 45 adult ICU patients with concurrent creatinine and cystatin C measurements within 24 hours of timed urine collection.
- Measured creatinine clearance (mCrCL) from timed urine collection served as the reference standard.
- Bias was calculated as the mean difference between estimated glomerular filtration rates (eGFRcr-cys and CG-CrCL) and mCrCL, with eGFR adjusted for body surface area (BSA).
Main Results:
- The mean bias between CG-CrCL and mCrCL was 23.8 mL/min.
- The mean bias between eGFRcr-cys and mCrCL was 3.3 mL/min.
- The difference in bias between the two methods was statistically significant (20.5 mL/min, P=.001), favoring eGFRcr-cys.
Conclusions:
- The cystatin C-based eGFRcr-cys calculation demonstrated significantly less bias than the CG-CrCL equation in estimating renal clearance in critically ill patients.
- Further investigation is warranted to explore the clinical utility of eGFRcr-cys over CG-CrCL, especially for medication-related decisions in this patient population.
Background:
Creatinine-based estimation equations for renal function, especially the Cockcroft-Gault creatinine clearance (CG-CrCL) equation, may be inaccurate in critically ill patients. We sought to determine if a cystatin C (CysC)-based (CKD-EPI CysC-serum creatinine (SCr) estimated glomerular filtration rate [eGFRcr-cys]) calculation better estimated renal clearance compared to CG-CrCL against measured creatinine clearance (mCrCL) from timed urine creatinine collection in adult critically ill patients.
Materials And Methods:
This was a single-center retrospective cohort study of adult patients admitted to an intensive care unit (ICU) between July 1, 2022, and July 31, 2023, who had concurrent creatinine and cystatin C measured within 24 hours of a timed urine creatinine collection. The primary outcome was the mean difference in bias between eGFRcr-cys and C-G CrCL compared to timed urine creatinine collection. eGFR was adjusted for body surface area (BSA) and reported as mL/min.
Results:
Forty-five patients were included in this study. The mean bias between C-G CrCL and mCrCL was 23.8 mL/min (95% CI -40.3 to 87.8 mL/min) and 3.3 mL/min (95% CI -43.3 to 49.9 mL/min) between eGFRcr-cys and mCrCL. The mean difference between the biases was 20.5 mL/min (P = .001).
Conclusions:
In critically ill patients, eGFRcr-cys was subject to less bias compared to C-G CrCL. Future research is needed to better understand the clinical implications of using eGFRcr-cys over C-G CrCL, particularly for medication-related decision making in critically ill patients.
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