The present invention provides methods for detecting the presence of or determining the amount of a ligand in a fluid sample. The methods comprise providing a first reagent comprising a sol particle having a detectable physical property bound to the ligand or ligand analogue (in a competitive format)...http://www.google.com/patents/US5851777?utm_source=gb-gplus-sharePatent US5851777 - Homogeneous sol-sol assay
