AFP ELISA Assay Kit is based on simultaneous binding of human AFP to two monoclonal antibodies, one immobilized on microwell plates, the other conjugated with horseradish peroxidase (HRP). After incubation, the separation bound-free is obtained with a simple solid-phase washing. Then the enzyme HRP in the bound-fraction reacts with the Substrate (H2O2) and the TMB Substrate and develops a blue color that changes into yellow when the Stop Solution (H2SO4) is added. The color intensity is proportional to the AFP concentration in the sample. The AFP concentration in the sample is calculated through a calibration curve. Sample Types: serum, plasma. Range: 5 -200 ng/ml. Sensitivity: 0.35 ng/ml. Time: 1.5 hours ? Alpha Fetoprotein (AFP) is a 68 kDa glycoprotein, which is normally only produced in the fetus during its development. It is a normally produced by the liver and yolk sac of the fetus. AFP levels decrease soon after birth and probably has no function in normal adults. It binds the hormone estradiol to keep it from affecting the fetal brain. Its measurement during pregnancy has been useful to detect certain abnormalities - specifically, if high levels of AFP are found in amniotic fluid, it can indicate a developmental defect in the baby.