Alkali resistant haemoglobin is -

Ans. is 'c' i.e., HbF* Adult haemoglobin is made up of a2b2* Foetal haemoglobin is made up of a2g2* Adult haemoglobin undergoes denaturation in the presence of alkali to form alkaline hematin. Alkaline hematin is insoluble and precipitates.* On the contrary foetal haemoglobin is resistant to alkali denaturation.* This is the basis of estimation of foetal haemoglobin, wherein HbF is quantitated by measuring the hemoglobin concentration before and after denaturation.* It is also the basis of alkali denaturation test or Apt test or Apt - Downey test used to differentiate foetal blood from maternal blood in a new born stool or vomitus.* After treatment with alkali, foetal hemoglobin will appear as a pinkish colour under the microscope while the adult hemoglobin will appear as a yellow-brownish colour.* A positive result is when pink colour is observed and is diagnosed as foetal bleeding.* A negative result is when yellow brownish colour is observed and is diagnosed as the neonatal swallowing of maternal blood.