Patent ID: 7256008

Claim:
A method for determining the amount of FK778 in a test sample comprising the steps of: (a) incubating a mixture comprising a test sample suspected of containing FK778, a solid phase coupled to an antibody specific for a first hapten, a bihapten comprising FK778 or an analogue of FK778 and the first hapten, and a reagent mixture comprising an antibody to FK778 conjugated to a label and an antibody to FK778 not conjugated to a label, wherein the ratio of the antibody to FK778 conjugated to a label to the antibody to FK778 not conjugated to a label in the reagent mixture ranges from about 1:135 to about 1:225, to form a detectable complex comprising (i) the antibody to FK778 conjugated to the label, (ii) a bihapten comprising a first hapten and FK778 or an analogue of FK778, and (iii) the solid phase coupled to the antibody specific for the first hapten; (b) separating the solid phase from the mixture; (c) measuring the amount of label bound to the solid phase; and (d) determining the amount of FK778 in the test sample from the amount of label measured.