Reagent used in Apt test

Alkali denaturation test (Apt-Downey test / apt test)Used to detect differentiate Fetal or neonatal blood from maternal blood (Qualitative).PrincipleMethodFetal hemoglobin (alpha 2 gamma 2 subunits) is resistant to alkali (basic) denaturation, whereas adult hemoglobin (alpha2 beta 2 subunits) is susceptible to such denaturation.Exposing the blood specimen to sodium hydroxide (NaOH) will denature the adult but NOT the fetal hemoglobin.The fetal hemoglobin will appear as a pinkish color under the microscope while the adult hemoglobin will appear as a yellow-brownish colorThe blood is mixed with sterile water to cause hemolysis of the RBCs, yielding free hemoglobin,The 5 ml pink hemoglobin-containing supernatant is then mixed with 1 mL of 1% NaOH.Fetal hemoglobin will stay pink and adult hemoglobin will turn yellow-brown.Adult hemoglobin changes color because it is less stable and will conve to hematin.