Patent ID: 7563622

Claim:
An immunoassay method to detect an analyte endogenous to a biological fluid sample wherein said sample also contains an exogenous material selected from the group consisting of cannabis, cocaine, and derivatives thereof capable of interfering with detection and measurement of said endogenous analyte in said fluid sample, comprising the steps of: A. Obtaining said biological fluid sample from an individual who has been exposed to said exogenous material, or a metabolite of said exogenous material, capable of interfering in analysis of said fluid for said endogenous analyte; B. Pretreating said biological fluid sample with an interferant suppression effective amount of a molybdenum complex to reduce manifestation of the presence of said exogenous material under assay conditions for said endogenous analyte without removing said exogenous material or said metabolite of said exogenous material from said biological fluid sample, said molybdenum complex formed from a molybdate compound and an oxyanion of phosphoric acid and present in said sample at a concentration of from about 5×10 −6 to 5×10 −3 mM; and C. Subjecting said fluid sample of Step (B) to immunoassay for said endogenous analyte.