Thromboxane A2 (TXA2), produced from arachidonic acid, causes irreversible platelet aggregation and contraction of vascular and bronchial smooth muscle. TXA2 is rapidly hydrolyzed non-enzymatically to TXB2, which is then quickly metabolized to urinary metabolites for clearance by the kidneys. Urinary analysis of TXB2 accurately reflects intrarenal TXA2 synthesis, while measurement of 11-dehydro and 2,3-dinor TX metabolites gives the best estimate of systemic TXA2 secretion. Cayman's TXB2 Express ELISA is a competitive assay that provides a rapid, accurate measurement of TXB2 from plasma, urine, and cell culture supernatants. The assay has a range from 15.6-2,000 pg/ml and a sensitivity (80% B/B0) of approximately 45 pg/ml.