The invention provides general methods for adjusting the inherent quantification range of a particular set of analytes in assays that employ capture reagents immobilized on solid supports. Specifically, the quantification range of a given analyte is adjusted to higher concentration regions by the addition of free capture reagent specific for that analyte, leaving the range of the remaining analytes the same and thereby permitting the simultaneous and accurate quantification of a plurality of analytes over a wide range of concentration values.