#$%^&*AU2015205899B220170511.pdf#####ABSTRACT The invention provides an ELISA assay for the determination of serum mast cell tryptase levels using rabbit anti-tryptase as the capture antibody and alkaline phosphatase conjugated G3 as the detecting antibody. Luminescent substrate CPSD was 5 used to enhance the assay sensitivity. Also provided are methods for aiding in the diagnosis of irritable bowel syndrome by detecting the serum level of -tryptase, histamine and/or prostaglandin E2.