The test principle applied in this kit is Sandwich enzyme immunoassay. The microtiter plate provided in this kit has been pre-coated with an antibody specific to Sepiapterin Reductase (SPR). Standards or samples are then added to the appropriate microtiter plate wells with a biotin-conjugated antibody specific to Sepiapterin Reductase (SPR). Next, Avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well and incubated. After TMB substrate solution is added, only those we