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

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 ±â€¯13 years, 49% of women) were included. Mean mGFR was 77 ±â€¯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: eGFRPOC = -0.1 (95% CI: -7.4; 3.0) + 1.06 (95% CI: 1.00; 1.15) x eGFRCOBAS. Mean bias was 3.7 ±â€¯14.1 mL/min/1.73m2. Concordance within 30% was 82%. Compared to mGFR, Passing-Bablok with POC was: eGFRPOC = -11.5 (95% CI: -22.9; -0.7) + 1.15 (95% CI: 1.02; 1.29) x mGFR. Mean bias was 0.1 ±â€¯17.6 mL/min/1.73m2. Accuracy within 30% was 81%. Between eGFRCOBAS and mGFR, mean bias was -3.7 ±â€¯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.

Technical and clinical evaluation of the VITROS® Immunodiagnostic Products 25-OH Vitamin D Total Assay--comparison with marketed automated immunoassays and a liquid chromatography-tandem mass spectrometry method.

BACKGROUND: The study was conducted to evaluate the technical and clinical performance of the VITROS® Immunodiagnostic Products 25-OH Vitamin D Total Assay, and compare it with the performance of five marketed automated assays and a liquid chromatography/mass spectrometry reference method (LC-MS/MS). METHODS: Three hundred patient serum samples were used to compare the correlation of the VITROS® 25-OH Vitamin D Total Assay with both the other immunoassays and the LC-MS/MS method, using Passing-Bablok regression and Bland-Altman analyses. Concordance of the diagnosis of vitamin D status was calculated to test the agreement between the different assays. In addition, samples containing vitamin D2 were used to test the assay's ability to detect the D2 form of the vitamin. RESULTS AND CONCLUSIONS: These results from the VITROS® 25-OH Vitamin D Total Assay generally correlated well with those from most of the marketed immunoassays. Cross-reactivity of the D2 form was calculated as being close to 100%. Additionally, we found substantial variability in performance amongst the various assays, which suggests the need for optimisation and recalibration of commercial methods.