Leukotriene E4 (LTE4) is a product of the 5-lipoxygenase (5-LO) pathway in activated mast cells, eosinophils, and monocytes. LTA4, the primary 5-LO metabolite, is rapidly converted to LTC4 and sequentially to LTD4 and LTE4. While plasma levels of LTC4 are virtually undetectable, exogenously administered LTC4 is recovered in the urine as LTE4 (5-13%) and two prominent oxidized metabolites resulting from several cycles of β-oxidation. Cayman’s LTE4 ELISA Kit is a competitive assay developed for the measurement of LTE4 from urine without a purification step. The assay has a range of 7.8-1,000 pg/ml and a sensitivity (80% B/B0) of approximately 25 pg/ml. This “dilute and go” format has been used successfully to demonstrate significant and reproducible changes in LTE4 levels in the urine of asthmatic patients after antigen challenge. If your samples require additional purification prior to analysis, Cayman’s Cysteinyl Leukotriene Affinity Sorbent (Item No. 400396) can be used for this purpose.