Highly specific, sensitive and rapid enzyme immunoassays for the measurement of acetaminophen in serum

Acetaminophen antibodies were purified using affinity chromatography and labelled with horseradish peroxidase (HRP). The antibody-HRP conjugate and a new acetaminophen derivative were used in the construction of two immunoassay methods facilitating the direct quantitative measurement of acetaminophen in serum: a 96-well microtitre plate and coated-tube ELISAs. A minimum detection limit of 0.2 mu g mL(-1) and a dynamic range of 0.2 to 10 mu g mL(-1) in serum were achieved using the 96-well microtitre plate ELISA. The tube assay was optimised for the measurement of the clinically critical acetaminophen concentration of 50 to 250 mu g mL(-1) of serum. The quantitative and specific tests could be completed within less than an hour. Common drugs including aspirin showed less than 0.1% cross-reactivity.