An evaluation of a C-reactive protein assay using a rate immunonephelometric procedure

By using 20 repetitive assays at three levels of C-reactive protein control serum, within-run and day-to-day precision of a rate immunonephelometric system was established. The precision was excellent in each case. Linearity of the system between 1.8 and 20 mg/dl was established at a coefficient of correlation of 0.999 by using serial dilutions of C-reactive protein control serum. When the immunonephelometric assay was compared with electroimmunodiffusion and radial immunodiffusion assays, coefficients of correlation of 0.986 and 0.993, respectively, were obtained. The lower limit of sensitivity of the immunonephelometric assay was 1.8 mg/dl. The relationship of clinical significance to the performance of the C-reactive protein test system using rate immunonephelometry is discussed.