The application discloses methods for simultaneous detection and quantifying multiple target analytes, including immunoglobulin isotypes and sub-classes, single and multiple protein antibodies within a test sample in a single reaction vessel. The method uses reaction wells as on a multi-well plate, each single well comprising microarrays of: calibration spots, having a predetermined quantity of a target analyte; and capture spots, having multiple agent antibodies, including isotypes and subclasses that specifically bind the target analytes. The captured analytes and the calibration spots are detected with fluorescently labeled antibodies specific for each analyte. The application also discloses methods for detecting and quantifying biomarkers, therapeutic proteins and patient derived antibodies; the use of secondary reagents to determine immunoglobulin classes Ig G, A, M, E and sub-classes including IgG1, IgG2, IgG3, IgG4 and IgA. The intensity of each fluorescent signal allows measurement of a specific immune response to a therapeutic protein and associated analytes.