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Nephrologists Make the Case for Cystatin C-Based eGFR
A patient's estimated glomerular filtration rate (eGFR) remains a pillar for diagnosing chronic kidney disease (CKD) and tracking its progression. But nephrologists now recognize that eGFR values based entirely on measurement of serum creatinine, the common approach, may be misleading because of nonrenal factors that can skew serum creatinine levels up or down.
The solution, they say, is to complement eGFR calculations based on serum creatinine (eGFRSCr) with a second calculation of eGFR based on serum levels of cystatin C (eGFRCysC), especially for patients in whom a modest change in eGFR could make a significant difference in both their stage of CKD and clinical management.
During a recent webinar organized by the American Kidney Fund, advocates for a more systematic role for eGFRCysC voiced hope that this approach will gain traction in US practice as cystatin C testing becomes more available and more widely recommended.
Cystatin C Can Be Used for a "Second Opinion", to Avoid Factoring in Race
"Cystatin C has fewer nonrenal determinants than creatinine," which means it is less likely to be affected by variables such as muscle mass, activity level, and diet, said Michelle M. Estrella, MD, chief of the Division of Nephrology at the San Francisco VA Healthcare System, California, during the webinar.
She encouraged clinicians to consider ordering a cystatin C test for a "second opinion" eGFR for patients with an eGFRSCr of 30-59 mL/min/1.73m2 to confirm or rule out stage 3 CKD; in those with conditions known to affect eGFRSCr; and in those with conditions that place them at increased risk for CKD progression such as diabetes, hypertension, cardiovascular disease, or heart failure.
Michael G. Shilpak, MD, a nephrologist at the University of California, San Francisco, agreed with these targeted subgroups for routine calculation of eGFRCysC. Measuring eGFRCysC "can have a substantial impact on patient safety," he said during the webinar.
Study results published by Shilpak several years ago documented the role cystatin C measurement can play in refining the diagnosis and prognosis of CKD.
"Use of cystatin C to calculate the eGFR strengthened the associations between eGFR categories and the risks of death and end-stage renal disease across diverse populations," Shilpak and colleagues wrote.
Nephrologists Make the Case for Cystatin C-Based eGFR
A patient's estimated glomerular filtration rate (eGFR) remains a pillar for diagnosing chronic kidney disease (CKD) and tracking its progression. But nephrologists now recognize that eGFR values based entirely on measurement of serum creatinine, the common approach, may be misleading because of nonrenal factors that can skew serum creatinine levels up or down.
The solution, they say, is to complement eGFR calculations based on serum creatinine (eGFRSCr) with a second calculation of eGFR based on serum levels of cystatin C (eGFRCysC), especially for patients in whom a modest change in eGFR could make a significant difference in both their stage of CKD and clinical management.
During a recent webinar organized by the American Kidney Fund, advocates for a more systematic role for eGFRCysC voiced hope that this approach will gain traction in US practice as cystatin C testing becomes more available and more widely recommended.
Cystatin C Can Be Used for a "Second Opinion", to Avoid Factoring in Race
"Cystatin C has fewer nonrenal determinants than creatinine," which means it is less likely to be affected by variables such as muscle mass, activity level, and diet, said Michelle M. Estrella, MD, chief of the Division of Nephrology at the San Francisco VA Healthcare System, California, during the webinar.
She encouraged clinicians to consider ordering a cystatin C test for a "second opinion" eGFR for patients with an eGFRSCr of 30-59 mL/min/1.73m2 to confirm or rule out stage 3 CKD; in those with conditions known to affect eGFRSCr; and in those with conditions that place them at increased risk for CKD progression such as diabetes, hypertension, cardiovascular disease, or heart failure.
Michael G. Shilpak, MD, a nephrologist at the University of California, San Francisco, agreed with these targeted subgroups for routine calculation of eGFRCysC. Measuring eGFRCysC "can have a substantial impact on patient safety," he said during the webinar.
Study results published by Shilpak several years ago documented the role cystatin C measurement can play in refining the diagnosis and prognosis of CKD.
"Use of cystatin C to calculate the eGFR strengthened the associations between eGFR categories and the risks of death and end-stage renal disease across diverse populations," Shilpak and colleagues wrote.
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