CRP is a hepatic acute-phase reactant protein, which is primarily induced by the interleukin-6 action due to an inflammatory/infectious process. Precision is closeness of agreement between indications or measured quantity values obtained by replicate measurements on the same or similar objects under specified conditions. Precision goals should be stated as the maximum allowable imprecision, SD, and/or CV expressed as a percentage (% CV) at each analyte´s concentration to be tested. The aim of this study was to verify the two different manufacturers' claims on C-reactive protein (CRP) based on the Clinical and Laboratory Standards Institute (CLSI) EP 15-A3 document.