Abstract: The present invention provides a method of making an assay device for conducting an assay to detect a concentration of an analyte in a sample fluid. The assay devices would typically have a substantially planar surface having a series of site specific immobilized calibration spot arrays containing pre-determined quantities of the analyte printed thereon. In addition, a series of site specific immobilized test spot arrays, including capture antibody for binding the analyte protein is printed on the assay device. The method involves first modifying the planar surface to provide hydrophobic binding sites, hydrophilic linking and covalent bonding sites. Then the method requires printing the series of site specific immobilized test spot arrays and the series of site specific immobilized calibration spot arrays on the substantially planar surface.