Potential interference of in vitro carbamylation on C-reactive protein laboratory measurement

Abstract

Carbamylation is a nonenzymatic post-translational modification observed during the reaction between cyanate and amino acids and/or proteins that may occur during some pathologies such as chronic kidney disease. Evidence suggests that carbamylation may interfere with the quantification of some analytes measured using immunoturbidimetric assays. C-reactive protein (CRP) is an inflammatory response protein that is commonly quantified through immunoturbidimetry in clinical laboratories. Because the presence of modified proteins in serum can lead to impaired quantification, this study aimed to verify the impact of in vitro carbamylation on the measurement of CRP in a CRP standard solution and serum pool. The samples were incubated with 150 nM, 150 µM, or 150 mM potassium cyanate (KOCN) or 20, 100, or 500 mg/dL urea at 37 °C for 24 h. CRP concentrations were measured using an immunoturbidimetric assay. The results showed a 61%–72% decrease in the CRP detection rate after incubation with KOCN. Incubation with urea resulted in a 0.7%–8% lower CRP detection rate. The results of this study indicate that high concentrations of cyanate can lead to falsely decreased CRP levels, as measured by immunoturbidimetry.

Keywords:

• C-reactive protein
• protein carbamylation
• immunoturbidimetry
• biomarkers
• assay interference

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Carolina dos Santos Stein received a research scholarship from the Coordination for the Improvement of Higher Education Personnel (CAPES/Brazil - Finance Code 001). Rafael Noal Moresco received a research productivity scholarship from the National Council for Scientific and Technological Development [CNPq, Brazil, number 313379/2021-1]. Conselho Nacional de Desenvolvimento Científico e Tecnológico;Coordenação de Aperfeiçoamento de Pessoal de Nível Superior.