Reference interval for serum C-reactive protein in healthy blood donors using the Dade Behring N Latex CRP mono assay

Measurement of the serum concentration of the acute-phase reactant C-reactive protein (CRP) provides an useful objective marker in clinical practice, both in screening for diseases and in monitoring disease activity and response to therapy. The aim of this study was to evaluate the analytical performance of the assay in the concentration range from 0.2 to 15 mg/L, and to determine a reference interval for serum CRP in healthy blood donors using the Dade Behring N Latex CRP mono assay on the Dade Behring Nephelometer II. The assay is a particle-enhanced nephelometric immunoassay with a measuring range of 0.2-1100 mg/L. The sample volume is 40 microL, and the assay time is 6 min. The coefficients of variation for within-run and between-run imprecision studies were between 2.2 and 5.4% in serum pools with CRP concentrations between 1.29 and 11.98 mg/L. Linearity studies showed excellent correlation between the theoretical and the measured values. No interferences were detected from hemoglobin <1.0 mmol/L, bilirubin <512 micromol/L and Intralipid <20 g/L. Blood samples were collected from 268 healthy blood donors (107 females and 161 males) between 20 and 65 years old. The non-parametric reference intervals for serum CRP was calculated to be <0.2-14.7 mg/L in females and <0.2-9.16 mg/L in males. The Mann-Whitney U-test revealed no gender-related difference for serum CRP (p-value=0.72). A common reference interval for serum CRP for both genders was calculated to be <0.2-10.5 mg/L (median 0.98 mg/L, range <0.2-17.3 mg/L).