Methods, compositions and kits are disclosed. The methods are directed to
determining the presence of one or more analytes in a sample suspected of
containing any one of a plurality of the analytes. A combination is
provided comprising in a medium (i) the sample, (ii) a binding partner for
each of the analytes, (iii) for each of the analytes, a first reagent
comprising a member of a signal producing system, a ligand and an analyte
analog, and (iv) a second reagent comprising a binding partner for the
ligand. The binding of the binding partner for the ligand is affected by
the presence of an analyte and alters the amount of signal produced by the
member of the signal producing system. The signal thus is modulated if one
or more of the analytes are present in the sample. The amount of the
signal is determined and is related to the presence of one or more of the
analytes in the sample. The method may be homogeneous or heterogeneous.
