Performance of Cystatin C- and Creatinine-Based Estimated Glomerular Filtration Rate Equations Depends on Patient Characteristics

BACKGROUND: The Kidney Disease Improving Global Outcomes (KDIGO) guideline recommends use of a cystatin C-based estimated glomerular filtration rate (eGFR) to confirm creatinine-based eGFR between 45 and 59mL center dot min(-1)center dot(1.73 m(2))(-1). Prior studies have demonstrated that comorbidities such as solid-organ transplant strongly influence the relationship between measured GFR, creatinine, and cystatin C. Our objective was to evaluate the performance of cystatin C based eGFR equations compared with creatinine-based eGFR and measured GFR across different clinical presentations. METHODS: We compared the performance of the CKD-EPI 2009 creatinine-based estimated GFR equation (eGFR(Cr)) and the newer CKD-EPI 2012 cystatin C based equations (eGFR(Cys) and eGFR(Cr-Cys)) with measured GFR (iothalamate renal clearance) across defined patient populations. Patients (n = 1652) were categorized as transplant recipients (n = 568 kidney; n = 319 other organ), known chronic kidney disease (CKD) patients (n = 618), or potential kidney donors (n = 147). RESULTS: eGFR(Cr-Cys), showed the most consistent performance across different clinical populations. Among potential kidney donors without CKD [stage 2 or higher; eGFR >60 mL center dot min(-1) center dot(1.73 m(2))(-1)], eGFR(Cys) and eGFR(Cr-Cys), demonstrated significantly less bias than eGFR(Cr); however, all 3 equations substantially underes-timated GFR when eGFR was <60 mL center dot min(-1)center dot(1.73 m(2))(-1). Among transplant recipients with CKD stage 3B or greater [eGFR <45 mL center dot min(-1) center dot (1.73 m(2))(-1)], eGFR(Cys), was significantly more biased than eGFR(Cr). No clear differences in eGFR bias between equations were observed among known CKD patients regardless of eGFR range or in any patient group with a GFR between 45 and 59 mL center dot min(-1) center dot(1.73 m(2))(-1). CONCLUSIONS: The performance of eGFR equations depends on patient characteristics that are readily apparent on presentation. Among the 3 CKD-EPI equations, eGFR(Cr-Cys) performed most consistently across the studied patient populations. (C) 2015 American Association for Clinical Chemistry