A new homogeneous immunoassay of whole blood C-reactive protein based on the use of magnetic field-assisted agglutination of polyclonal anti-CRP coated superparamagnetic particles is described. These particles self-organize into linear chains under an appropriate magnetic field which considerably increase the colliding frequency and thus, the probability to form links between ligand and receptor. Therefore, reaction rates are highly accelerated so that results are obtained well before the system has reached equilibrium. This immunoassay can be adapted to perform high sensitivity as well as high speed assays depending on analyte concentration. The high capabilities of magnetic agglutination immunoassay allow the integration of a whole blood CRP immunoassay to an existing high speed hematology analyzer. The feasibility of such a concept is reported with a prototype that combines the sampling process of a hematology analyzer with an immunodetection module. As a result, a complete whole blood CRP analysis cycle is achieved in less than one minute. The successful application of these investigations should reinforce the competitiveness and leading position of HORIBA medical in whole blood immunoassay.