Abstract: This invention relates to a method for determining the concentration/amount of analyte molecules in the sample. The method has at least the following steps: a) adding to the sample a known concentration/amount of competitor or analogue molecules of the analyte, which are distinct from the analyte molecules, b) reacting/contacting the sample of step a) with capture molecules for the analyte and competitor molecules, c) determining a measure for the ratio R of analyte and competitor molecules that are bound to the capture molecules, d)determining the concentration/amount of the analyte molecules from the ratio R of step c) and the known concentration/amount of competitor molecules in the sample of step a).