Methods and apparatus for stabilization of aggregation-based assays are described. In various embodiments, anti-analytes are dispersed within a matrix. A solution containing analytes brought into contact with the matrix, so that analytes may permeate throughout at least a portion of the matrix. In some embodiments, the anti-analytes and analytes are mobile within the matrix. As aggregates form and increase in size, the aggregates become substantially immobile within the matrix. As a result, signals representative of an amount of aggregation within the matrix can remain substantially constant. In various aspects, matrix-stabilized aggregation-based assays provide for reliable quantitative analysis of analyte concentration with test solutions.