Henry Ford Hospital Medical Journal


C-reactive protein (CRP) determinations in serum have been evaluated by two methods: the capillary tube method (presently in use) and the double diffusion technic (a newly developed procedure standardized in this laboratory). Advantages of the double diffusion technic are (1) quantitation of CRP in milligrams per 100 ml of serum, (2) differentiation of CRP from non-specific precipitates often found in patients' sera, and (3) increased sensitivity. A normal range of CRP levels has been established by analyzing serum from 750 supposedly healthy blood bank donors. Ninety-five percent of the donor population possess less than 1.0 mg of CRP per 100 ml of serum (53% are negative, 23% with trace quantities and 19% with 0.2-1.0 mg per 100 ml of serum). CRP serum levels above 1.0 mg per 100 ml are significant values for clinical interpretation.