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Estimated GFR With Cystatin C and Creatinine in Clinical Practice: A Retrospective Cohort Study
Eric Raphael Gottlieb1,2,3, Christopher Estiverne2,4, Nicole V Tolan2,5
1Department of Medicine, Mount Auburn Hospital, Cambridge, Massachusetts.
Insights
Cystatin C eGFR strongly correlates with creatinine eGFR but significantly impacts chronic kidney disease (CKD) staging for many patients. Understanding this effect is crucial as cystatin C use increases in clinical practice.
Area of Science:
- Nephrology
- Biomarker Research
- Clinical Chemistry
Background:
- Accurate estimation of glomerular filtration rate (eGFR) and chronic kidney disease (CKD) staging are critical for patient management.
- Creatinine-based eGFR is standard, but a national task force recommends cystatin C for confirmation.
- The clinical impact of cystatin C on CKD staging requires further investigation.
Purpose of the Study:
- To assess the correlation between cystatin C-based eGFR and creatinine-based eGFR.
- To determine how cystatin C influences CKD staging compared to creatinine.
- To evaluate the potential effects of cystatin C adoption on kidney care delivery.
Main Methods:
- Retrospective observational cohort study of 1,783 inpatients and outpatients.
- Analysis included serum creatinine, cystatin C levels, and basic clinical/sociodemographic variables.
- Univariate and multivariable linear and logistic regression models were employed.
Main Results:
- Cystatin C eGFR showed a strong correlation with creatinine eGFR (Spearman ρ = 0.83).
- Cystatin C eGFR led to a change in CKD stage for 34% of patients (27% later, 7% earlier).
- Black race was associated with a lower likelihood of stage change, while age and Elixhauser score increased this likelihood.
Conclusions:
- Cystatin C eGFR is strongly correlated with creatinine eGFR.
- Cystatin C significantly impacts CKD staging, necessitating clinician awareness.
- The findings highlight the importance of understanding cystatin C's role in kidney disease management.
Rationale & Objective:
Estimation of glomerular filtration rate (eGFR) and staging of chronic kidney disease (CKD) are essential to guide management. Although creatinine is routinely used, a recent national task force recommended the use of cystatin C for confirmation. The objective of this study was to examine the following parameters: (1) how cystatin C correlates with creatinine eGFR; (2) how it indicates differences in CKD staging; and (3) how it may affect kidney care delivery.
Study Design:
Retrospective observational cohort study.
Setting & Participants:
1,783 inpatients and outpatients who had cystatin C and creatinine levels drawn within 24 hours at Brigham Health-affiliated clinical laboratories.
Predictors:
Serum creatinine levels, basic clinical/sociodemographic variables, and reasons for ordering cystatin C from a structured partial chart review.
Analytical Approach:
Univariate and multivariable linear and logistic regression.
Results:
Cystatin C-based eGFR was very strongly correlated with creatinine-based eGFR (Spearman correlation ρ = 0.83). Cystatin C eGFR resulted in a change to a later CKD stage in 27%, an earlier stage in 7%, and no change in 66% of patients. Black race was associated with a lower likelihood of change to a later stage (OR, 0.53; 95% CI [0.36, 0.75]; P < 0.001), whereas age (OR per year OR, 1.03; 95% CI [1.02, 1.04]; P < 0.001) and Elixhauser score (OR per point OR, 1.22; 95% CI [1.10, 1.36]; P < 0.001) were associated with a higher likelihood of change to a later stage.
Limitations:
Single center, no direct measurement of clearance for comparison, and inconsistent self-identification of race/ethnicity.
Conclusions:
Cystatin C eGFR correlates strongly with creatinine eGFR but can have a substantial effect on CKD staging. As cystatin C is adopted, clinicians must be informed on this impact.
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