Estimated glomerular filtration rate using a point of care measure of creatinine in patients with iohexol determinate GFR

Abstract

Introduction: Determination of creatinine and estimation of Glomerular Filtration Rate (GFR) rapidly before injection of contrast media provides early detection of high-risk patients for acute kidney failure. Hence, a rapid point-of-care (POC) device (result in 30 s) allowing creatinine measurement and eGFR could be of interest. To validate this method, we considered a population referred for measuring GFR.

Methods: Iohexol plasma clearance was used to measure GFR. For each subject, enzymatic creatinine was quantified with two different devices: in plasma with the Roche Cobas analyzer and in capillary blood with the Nova Biomedical POC device. Both values of creatinine were used in the CKD-EPI equation for estimated glomerular filtration rate (eGFR). eGFR using POC was compared to eGFR using Cobas and to mGFR by Passing Bablok regression, calculation of bias, precision and accuracy (or concordance) within 30%. Also, we calculated the rate of discrepant staging (eGFR >60 or ≤ 60 when mGFR is actually ≤60 and > 60) with both creatinine methods.

Results: 120 subjects (52 ± 13 years, 49% of women) were included. Mean mGFR was 77 ± 27 mL/min/1.73m² with 29 patients presenting mGFR <60 mL/min/1.73m². Passing- Bablok regression comparing eGFR obtained with the POC and the Cobas was: eGFR_POC = -0.1 (95% CI: -7.4; 3.0) + 1.06 (95% CI: 1.00; 1.15) x eGFR_COBAS. Mean bias was 3.7 ± 14.1 mL/min/1.73m². Concordance within 30% was 82%. Compared to mGFR, Passing-Bablok with POC was: eGFR_POC = -11.5 (95% CI: -22.9; -0.7) + 1.15 (95% CI: 1.02; 1.29) x mGFR. Mean bias was 0.1 ± 17.6 mL/min/1.73m². Accuracy within 30% was 81%. Between eGFR_COBAS and mGFR, mean bias was -3.7 ± 12.5 mL/min/1.73m². Accuracy within 30% was 95%. With POC (and Cobas), 3.3% (0.8%) of patients would have been considered with GFR > 60 mL/min/1.73m² whereas mGFR it was ≤60 and 10% (9.2%) of them would have been considered with GFR ≤60 mL/min/1.73m² when mGFR was >60.

Conclusion: Creatinine measured with the POC has an acceptable performance when used with the CKD-EPI equation to estimate GFR. Its ability to detect GFR <60 mL/min/1.73m² is not significantly different from the classical Roche assay. StatSensor Creatinine (Nova Biomedical) can be used for GFR screening before contrast media injection.

Keywords: Creatinine; Glomerular filtration rate; Iohexol; Point of care.