A method and system for measuring agglutination in a target-induced agglutination assay with one or more magnetic particles is performed in a reaction chamber. After the magnetic particles, which are capable of binding to a target are provided in the assay, an agglutination process is performed resulting in agglutinated particles. Further an alternating current magnetic field (HAC) is applied to the assay. The method further includes measuring an effect of the HAC on the one or more magnetic particles unattached to any surface. The measured effect is indicative of one or more agglutination parameters.