[Assay of serum C-reactive protein. Comparison of 3 immunologic methods]

C-reactive protein is a parameter measured in ordinary laboratory routine and is frequently needed rapidly. The authors hereby compare three methods for the measurement of this protein using three common laboratory apparatus: TDX Abbott, BNA Behring and ICS Beckman. The experimental protocol used has been the one defined by the SFBC "Valtec" Commission. Regarding repeatability, the variation coefficients (CV%) are less than 10, except for a CRP value of 16 mg/l on TDX (19.3) and for a value of 56.4 mg/l on ICS (12.5). Reproducibility values confirm repeatability results in the case of TDX, while for ICS CV% are always less than 10. For values between 0 and 133 mg/l the authors have excellent linearity for the three apparatus tested (r = 0.99). The apparatus when compared two by two on 104 patient samples give linear allometric values and correlation coefficients are with acceptable limits (greater than 0.98). It must be noted that there is a difference between results obtained for patient samples and control sera when tested by the different apparatus. ICS necessitates daily calibration and gives the best values with control sera. With BNA the authors obtained more precise values and while TDX remains the easiest to handle, it gives unacceptable imprecise values for low CRP concentrations.