This assay employs the competitive inhibition enzyme immunoassay technique. The microtiter plate provided in this kit has been pre-coated with an antibody. Standards or samples are added to the appropriate microtiter plate wells with Horseradish Peroxidase (HRP) conjugated 1,25 DHVD3 Hapten. The competitive inhibition reaction is launched between with HRP-conjugated 1,25 DHVD3 Hapten and 1,25 DHVD3 in samples. A substrate solution is added to the wells and the color develops in opposite to the a