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Correlation of Measured and Estimated Creatinine Clearance in Hospitalized Elderly Patients: A Retrospective Cohort
Rachel I Lavelle1, Austin R Brown2, Anthony Gerlach1
1The Ohio State University Wexner Medical Center, Columbus, USA.
Insights
The Cockcroft-Gault (C-G) method significantly over- or underestimates creatinine clearance (CrCl) in elderly hospitalized patients. Measured CrCl is crucial for accurate renal function assessment in this population.
Area of Science:
- Nephrology
- Geriatric Medicine
- Clinical Pharmacology
Background:
- Accurate renal function assessment is critical for elderly hospitalized patients.
- Limited data exist on the accuracy of Cockcroft-Gault (C-G) estimates of creatinine clearance (CrCl) versus measured CrCl in this demographic.
- This study addresses the need for evaluating C-G estimates in hospitalized elderly individuals.
Purpose of the Study:
- To determine the correlation between C-G estimated CrCl and measured CrCl in hospitalized elderly patients.
- To assess the bias and precision of C-G estimates compared to measured CrCl.
- To identify potential discrepancies in renal function assessment using the C-G method.
Main Methods:
- Retrospective observational cohort study of patients aged 65 years and older admitted between January and September 2018.
- Inclusion criteria: 8- or 24-hour urine collection during admission.
- Primary outcome analysis: Pearson correlation, Spearman linear regression, and Bland-Altman analysis for C-G estimates versus measured CrCl, with outliers defined as >±20% difference.
Main Results:
- Study included 108 urine collections from 90 patients; median age 71 years, 51% female.
- Median C-G estimated CrCl was 75.4 mL/min, and median measured CrCl was 79.1 mL/min (r² = .56, P < .001).
- Bland-Altman analysis revealed wide limits of agreement (-75.5-57.7 mL/min), with significant bias (-8.9 mL/min) and precision (34 mL/min). 38% of C-G estimates were >120% and 18% were <80% of measured CrCl.
Conclusions:
- Measured CrCl demonstrates significant variability when compared to C-G estimates in hospitalized elderly patients.
- The findings highlight the potential for inaccurate renal function assessment using the C-G method in this population.
- Identifying patients who may benefit from direct measurement of CrCl is essential, and further research should explore the clinical impact of these variances.
Abstract:
Background: Accurate assessment of renal function is essential in hospitalized elderly patients. Few studies have examined the accuracy of Cockcroft-Gault (C-G) estimates of creatinine clearance (CrCl) compared with measured clearance in these patients. Objective: The objective of this study was to determine the correlation between C-G estimates of CrCl and measured CrCl in hospitalized elderly patients. Methods: This Institutional Review Board-approved, single-center retrospective observational cohort study included all patients who were 65 years and older admitted to our medical center in January to September 2018 with either an 8- or 24-hour urine collected during admission. The primary outcome was correlation, bias, and precision of C-G estimates of CrCl versus measured CrCl using Pearson correlation, Spearman linear regression, and Bland-Altman analysis. Outliers were determined using a cut-off of ±20%. Data are presented as median (interquartile range) or percentages. Results: A total of 108 urine collections from 90 unique patients were included in the study. The patients were 51% female, median age was 71 (68-77) years, and median body mass index was 26.6 (22.8-31) kg/m2. Most collections were over 24 hours (66.7%), and 38% were performed while patients were in an intensive care unit. Median blood urea nitrogen (BUN) was 24.5 (17-36) mg/dL and median serum creatinine was 0.71 (0.55-1.09) mg/dL. The median C-G estimation was 75.4 (48.2-110.6) mL/min, and the median measured CrCl was 79.1 (38.1-99.5) mL/min, r 2 = .56 (P < .001). Bland-Altman analysis showed large limits of agreement (-75.5-57.7 mL/min), with a bias of -8.9 and precision (standard deviation of bias) of 34 mL/min. Outliers were common, with 38% of C-G estimation values >120% of measured CrCl, and 18% of C-G estimates <80% of measured CrCl. Conclusions: Measured CrCl varied significantly from C-G estimates in hospitalized elderly patients. It is important to recognize characteristics of patients who may benefit from measurement of CrCl. Future studies should examine the impact of this variance on clinical outcomes.
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