Development of UME CRM 1008: certified reference material for C-reactive protein

A certified reference material (CRM) specifically designed for C-reactive protein (CRP) measurement in clinical laboratories was produced in this study. CRP, a protein synthesized by the liver, serves as an indicator of inflammation when present in elevated concentrations in the bloodstream. The primary goal is to ensure accurate measurement and quality control in accredited clinical laboratories. To achieve this, a recombinant CRP solution was selected as the most suitable candidate material for the CRM due to its exceptional purity. The homogeneity and stability of the developed CRM were thoroughly examined using size exclusion chromatography coupled with ultraviolet detection and high-performance liquid chromatography, (SEC-UV-HPLC). Additionally, traceable amino acid analysis coupled with isotope dilution mass spectrometry (ID-LC/MS-AAA) was employed to determine the protein concentration of CRP in the CRM solution. The evaluation of uncertainties originating from factors such as characterization, homogeneity, long-term stability, and short-term stability data was incorporated to assess the uncertainty associated with the certified CRP value. Consequently, the certified value of the CRM, denoted as UME CRM 1008, was determined to be 43.2 ± 2.2 μmol kg⁻¹, with an expanded uncertainty at a coverage factor of k = 2. The CRP-certified reference material resulting from this study is intended to be used as a primary reference material to enable SI traceable measurement of CRP.