This assay employs the competitive inhibition enzyme immunoassay technique. A monoclonal antibody specific to Orexin (OX) has been pre-coated onto a microplate. A competitive inhibition reaction is launched between biotin labeled Orexin (OX) and unlabeled Orexin (OX) (Standards or samples) with the pre-coated antibody specific to Orexin (OX). After incubation the unbound conjugate is washed off. Next, avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well and incubate