Anyone out there been involved in the development of latex aggregation assays to quantify antibody in serum?

We had considered the 5 uM latex beads (I think they were from IDC) with crosslinked antibody as a capture reagent for a "field" testing kit for leptospiral infections, but there were problems of variablity in amounts and crosslinking.
Many companies now have multiplexed assays for cytokines, growth factors and kinases that actually use different sizes of beads/fluorochrome combinatons to simulataneously measure multiple proteins - usually by fluorimetric or flow cytometric techniques.