A sensitive and specific negative ion chemical ionization mass spectrometric assay for the major urinary metabolite of PGD2 has been developed employing a chemically synthesized [18(0)4]-labelled internal standard. 2. The finding that increased urinary excretion of this metabolite occurs in a number of clinical situations suggests that the assay may prove to be a valuable tool to explore the role of PGD2 in the pathophysiology of human disease.
