Accuracy of GFR estimating equations combining standardized cystatin C and creatinine assays: a cross-sectional study in Sweden

Abstract

Combining cystatin C and creatinine assays improves GFR estimations with P30 ≥90% in adults. Reporting estimates of both single and combined marker equations in clinical settings makes it possible to assess the validity of the combined equation based on the agreement between the single marker equations.

Cystatin C standardization decreases assay variation and improves assessment of glomerular filtration rate

“…Mean age was slightly higher in the BIS population at baseline with 80.4 versus 78.5 years in the iohexol population. There were 53% females, 79% on antihypertensive medication, 26% were diabetics, and the mean BSA was 1.81 m 2 in the total BIS population; characteristics of the iohexol population were 43% females, 77% individuals with hypertension, 24% diabetics, and a mean BSA of 1.85 m 2 In Table 2 an overview of the three cysC assays and the two BIS study populations is displayed. …”

“…Mean difference of eGFRCKD-EPI compared to mGFR was 5±10 mL/min/1.73m 2 for Roche Gen2 and 5±11 mL/min/1.73m 2 for Siemens. There was no significant difference in bias, precision or accuracy between Siemens and Gen 2 for eGFRCKD-EPI as compared to mGFR (Table 3) For the CAPA equation, mean eGFR values were 67±19 mL/min/1.73m 2 with Roche Gen2 and 66±19 mL/min/1.73m 2 with Siemens.…”

“…The mean measured GFR was 60±16 mL/min/1.73m 2 . Mean difference of eGFRCKD-EPI compared to mGFR was 5±10 mL/min/1.73m 2 for Roche Gen2 and 5±11 mL/min/1.73m 2 for Siemens.…”

“…Large cohort studies have demonstrated the added value of cysC-based or combined (including both cysC and creatinine) equations over solely creatinine-based GFR equations [2][3][4]. Compared to serum creatinine, the main advantages of cysC are its lower dependency on muscular mass as well as superior predictability of mortality and ESRD risk [5][6][7].…”

“…Additionally, it has been shown that including cysC into GFR equations has led to higher accuracy of GFR estimates compared to measured GFR [3;4;8]. As a consequence the "kidney disease improving global outcome" (KDIGO) guidelines recommend to confirm the diagnosis of chronic kidney disease (CKD) using a cysC-based GFR equation in patients with a creatinine-based GFR value between 45 and 59ml/min/1.73m 2 In the context of estimating GFR, standardization of biomarker measurement methods is of outstanding importance. Several authors have illustrated the negative impact of lack of standardized calibration for GFR estimation based on both creatinine and/or cysC [9][10][11][12][13][14].…”