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Discrepancies between Cystatin C-Based and Creatinine-Based eGFR
Danielle K Farrington1, Aditya Surapaneni2,3, Kunihiro Matsushita2
1Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Insights
Discrepancies between cystatin C- and creatinine-based estimated glomerular filtration rate (eGFR) are common. A lower eGFRcys than eGFRcr indicates worse kidney health and increased risk of mortality and adverse outcomes.
Area of Science:
- Nephrology
- Clinical Chemistry
- Epidemiology
Background:
- Recent guidance recommends increased use of cystatin C for estimating glomerular filtration rate (GFR).
- Discrepancies between creatinine-based (eGFRcr) and cystatin C-based (eGFRcys) estimated GFR (eGFR) may indicate inaccurate GFR estimation by creatinine alone.
- Understanding risk factors and clinical implications of large eGFR discrepancies is crucial.
Purpose of the Study:
- To investigate the risk factors associated with significant eGFR discrepancies.
- To determine the clinical implications of these discrepancies on adverse health outcomes.
Main Methods:
- Analysis of data from the Atherosclerosis Risk in Communities Study, a 25-year prospective cohort study.
- eGFR discrepancy defined as eGFRcys 30% lower or higher than eGFRcr.
- Associations with kidney parameters and long-term outcomes (kidney failure, AKI, heart failure, death) assessed using regression and Cox models.
Main Results:
- The proportion of individuals with eGFRcys 30% lower than eGFRcr increased from 7% to 23% over the study period.
- Risk factors for lower eGFRcys included older age, female sex, non-Black race, higher eGFRcr, higher BMI, weight loss, and smoking.
- Individuals with lower eGFRcys exhibited more anemia, higher uric acid, FGF23, and phosphate levels, and increased risk of mortality, kidney failure, AKI, and heart failure.
Conclusions:
- A lower eGFRcys compared to eGFRcr is associated with poorer kidney-related laboratory results.
- This discrepancy signifies a higher risk of adverse health outcomes, including mortality and kidney failure.
Background:
Recent guidance suggests clinicians increase use of cystatin C for the estimation of GFR. Discrepant levels of creatinine- versus cystatin C-based eGFR (eGFRcr versus eGFRcys) can occur and might signify inaccurate estimation of GFR using creatinine alone. This study sought to enhance the knowledge of the risk factors and clinical implications of having a large eGFR discrepancy.
Methods:
Participants in the Atherosclerosis Risk in Communities Study, a prospective cohort study of US adults, were followed over 25 years. eGFR discrepancy was measured at five clinical visits and defined as eGFRcys either 30% lower or higher than eGFRcr, the current clinical standard of care. The associations between eGFR discrepancies and kidney-related laboratory parameters were assessed using linear and logistic regression and long-term adverse outcomes, including kidney failure, AKI, heart failure, and death, using Cox proportional hazards models.
Results:
Among 13,197 individuals (mean age 57 [SD 6] years, 56% women, 25% Black race), 7% had eGFRcys 30% lower than eGFRcr at visit 2 (1990-1992), and this proportion increased over time to 23% by visit 6 (2016-2017). By contrast, the percent with eGFRcys 30% higher than eGFRcr was relatively stable (3%-1%). Independent risk factors for having eGFRcys 30% lower than eGFRcr included older age, female sex, non-Black race, higher eGFRcr, higher body mass index, weight loss, and current smoking. Those with eGFRcys 30% lower than eGFRcr had more anemia and higher uric acid, fibroblast growth factor 23, and phosphate levels as well as higher risk of subsequent mortality, kidney failure, AKI, and heart failure compared with those with similar eGFRcr and eGFRcys values.
Conclusions:
Having eGFRcys lower than eGFRcr was associated with worse kidney-related laboratory derangements and a higher risk of adverse health outcomes.
Podcast:
This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/CJASN/2023_09_08_CJN0000000000000217.mp3.
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