Abstract: A system and method for determining the presence and/or concentration of one or more analytes in a sample that comprises a fluid, the system comprising a substrate comprising a sample inlet or inlets and one or more analyte determination flow paths, each analyte determination flow path comprising a defined beginning and a defined terminus and comprising at least one capture zone containing a capture agent for an analyte, the capture agent or agents being immobilized along a portion of the flow path or paths, the flow path or paths being designed so that the one or more analytes are depleted from the sample and bound to the portion of the flow path or paths containing immobilized capture agent or agents, producing an analyte depletion end region for each analyte between the beginning and the terminus of the analyte determination flow path.