Discordant Cystatin C vs Creatinine

Patients with an estimated glomerular filtration rate (eGFR) based on cystatin C (eGFRcys) that is 30% lower than their serum creatinine-based eGFR (eGFRcr) have worse cardiorenal outcomes. Michelle Estrella, MD, MHS, from the University of California, San Francisco, and San Francisco Veterans Affairs Health Care System, presented findings from a meta-analysis at the American Society of Nephrology’s Kidney Week and concurrently in JAMA. 

To assess the prevalence and implications of discordant eGFRs, Dr Estrella and her team examined data from 860,966 patients in the Chronic Kidney Disease (CKD) Prognosis Consortium (CKD-PC). The outcomes of interest were all-cause mortality and kidney and cardiovascular (CV) outcomes. An eGFRcys at least 30% lower or higher than eGFRcr was deemed clinically significant. 

The outpatients (n=821,327) and inpatients (n=39,639) were aged a mean 59 and 67 years and 48% and 31% were women, respectively. Mean eGFRcr was 87 and 69 mL/min/1.73m2, and mean eGFRcys was 81 and 57 mL/min/1.73m2, respectively.

Among outpatients, the median difference in eGFRs was -5.4%, in which 11.2% had a large negative difference between eGFRs and 3.8% had a large positive difference. For inpatients, the median difference in eGFRs was -15.4%, in which 35% had a large negative difference and 14.5% had a large positive difference. 

A higher proportion of patients with a large negative eGFR difference had lower eGFRcr values.

In both outpatients and inpatients, a large negative eGFR difference was associated with increased odds of 

Conflicting associations were observed for coronary heart disease, where outpatients had increased odds of a negative eGFR difference (aOR, 1.20) but inpatients had decreased odds (aOR, 0.78).

Among outpatients, a 30% or greater negative eGFR difference was associated with increased risks for