An improved assay for the determination of C-reactive protein

C-reactive protein as the most important acute phase reactant in clinical use provides information about acute as well as chronic inflammatory processes. This application requires an improvement of traditional assays that have been available to the clinical laboratory regarding lipemic interference, precision especially at the lower end, assay and calibration stability as well. In the present study the improved Olympus turbidimetric assay for the determination of C-reactive protein (CRP) was evaluated on the Olympus AU640 analytical system. The assay has a lower detection limit of 1.57 mg/l CRP and is linear from 5 mg/l to 200 mg/l. Prozone hook effect did not occur until 300 mg/l with increased prozone sample detection to 3500 mg/l. Imprecison CV values for within-run of less than 2.25% and between-day of lower than 3.1% were found. On-board stability was extended to 60 days, and calibration stability to 28 days. Method comparison to another automated CRP assay yielded a correlation coefficient of r=0.999. Endogenous substances did not interfere with the test results. There was satisfactory recovery of target values according to CRM 470 standardization. In comparison to the previous assay the improved assay offers more accuracy, precision, and linearity and is free from any known interference, which meets user needs, for rapid and convenient determination of CRP on automated analyzers.