Effect of serum creatinine difference between the Jaffe and the enzymatic method on kidney disease detection and staging

Point-of-care testing device platform for the determination of creatinine on an enzyme@CS/PB/MXene@AuNP-based screen-printed carbon electrode

Screen-printed carbon electrodes (SPCE) functionalized with MXene-based three-dimensional nanomaterials are reported for rapid determination of creatinine. Ti3C2TX MXene with in situ reduced AuNPs (MXene@AuNP) were used as a coreactant accelerator for efficient immobilization of enzymes. Creatinine could be oxidized by chitosan-embedded creatinine amidohydrolase, creatine amidinohydrolase, or sarcosine oxidase to generate H2O2, which could be electrochemically detected enhanced by Prussian blue (PB). The enzyme@CS/PB/MXene@AuNP/SPCE detected creatinine within the range 0.03-4.0 mM, with a limit of detection of 0.01 mM, with an average recovery of 96.8-103.7%. This indicates that the proposed biosensor is capable of detecting creatinine in a short amount of time (4 min) within a ± 5% percentage error, in contrast with the standard clinical colorimetric method. With this approach, reproducible and stable electrochemical responses could be achieved for determination of creatinine in serum, urine, or saliva. These results demonstrated its potential for deployment in resource-limited settings for early diagnosis and tracking the progression of chronic kidney disease (CKD).

Dopamine infusion at typical infusion rates does not cause interference on plasma creatinine assays

a Objectives

Dopamine is known to cause negative interference on enzymatic creatinine measurement. However, its effect on the Jaffe reaction, and its concentration required to interfere with enzymatic reactions, remain uncertain. This study was designed to study the interference of stable dopamine infusion on Jaffe and enzymatic creatinine assays, as well as the effect of dopamine infusion drip arm contamination on both creatinine assays.

b Design and Methods

For the first part of the study, dopamine was spiked into pooled plasma samples at different concentrations to mimic the scenario of patients on dopamine infusion at an infusion rate between 2 and 20 μg/kg/min. For the second part, dopamine preparation of 2 g/L (same as the preparation used clinically) was mixed with pooled plasma samples at different proportions to mimic drip arm contamination. Creatinine concentrations were measured using Jaffe and enzymatic reactions.

c Results

The first part showed that creatinine measurements were not interfered by dopamine infusion at an infusion rate between 2 and 20 μg/kg/min. The second part showed that dopamine could negatively interfere with enzymatic creatinine assays, even with minute drip arm contamination. The effect on the Jaffe reaction was less significant.

d Discussion

Creatinine concentration could be reliably measured by Jaffe or enzymatic reactions if samples are from venous access sites other than the site of dopamine infusion. When dopamine interference on enzymatic creatinine assays is suspected, using the Jaffe reaction to cross-check may provide additional useful information.

An improved implementation of metrological traceability concepts is needed to benefit from standardization of laboratory results

Non-harmonization of laboratory results represents a concrete risk for patient safety. To avoid harms, it is agreed that measurements by in vitro diagnostic medical devices (IVD-MD) on clinical samples should be traceable to higher-order references and adjusted to give the same result. However, metrological traceability is not a formal claim and has to be correctly implemented, which in practice does not happen for a non-negligible number of measurands. Stakeholders, such as higher-order reference providers, IVD manufacturers, and External Quality Assessment organizers, have major responsibilities and should improve their contribution by unambiguously and rigorously applying what is described in the International Organization for Standardization 17511:2020 standard and other documents provided by the international scientific bodies, such as Joint Committee on Traceability in Laboratory Medicine and IFCC. For their part, laboratory professionals should take responsibility to abandon non-selective methods and move to IVD-MDs displaying proper selectivity, which is one of the indispensable prerequisites for the correct implementation of metrological traceability. The practicality of metrological traceability concepts is not impossible but relevant education and appropriate training of all involved stakeholders are essential to obtain the expected benefits in terms of standardization.

Avoiding falsely low creatinine concentrations measured in patients treated with N-acetylcysteine for acetaminophen intoxication using enzymo-amperometric method - An in vitro and in vivo study

BACKGROUND

Circulating creatinine is a biomarker of paramount importance in clinical practice. In cases of acetaminophen (APAP) intoxication, the antidote, N-acetylcysteine (NAC), interferes with commonly used creatininase-peroxidase methods. This study aimed to assess whether creatininase-amperometric methods were affected in this context.

METHODS

This study includes in vitro interference tests, involving four creatinine assays using NAC-spiked plasma pools and an in vivo retrospective study comparing creatininase-peroxidase and creatininase-amperometric measurements in patients presenting with NAC-treated APAP poisoning.

RESULTS

Creatininase-peroxidase method was impacted by NAC interference in a clinically-significant manner at therapeutic NAC levels (basal value recovery of 80 % and 70 % for 500 and 1000 mg.L-1 of NAC, respectively), surpassing the desirable Reference Change Value (RCV%). Enzymo-amperometric methods were not impacted. Among patients, a mean bias of -45.2 ± 28.0 % was observed for the peroxidase detection method compared to the amperometric in those who received NAC prior plasma sampling and -2.7 ± 5.4 % in those who did not.

CONCLUSIONS

Our findings indicate that enzymo-amperometric creatinine assays remain unaffected by NAC interference due to the absence of the peroxidase step in the analytical process. Therefore, these methods are suitable to prevent spurious hypocreatininemia in APAP intoxicated patients undergoing NAC therapy.