The acid elution test or Kleihauer-Betke test is a semi-quantitative blood test for the detection of fetal hemoglobin (also: hemoglobin F, HbF) in blood smears by acid elution. Fetal haemoglobin estimates are made to determine possible bleeding in the newborn infant, in particular to avoid Rh incompatibility. The haemoglobin F-test is also used in adults as an aid in the diagnosis of certain forms of anaemia.
The Hemafix® -acid-elution-test or Kleihauer-Betke-test is based on the fact that haemoglobin F (HbF) is resistant to acid elution, whereas haemoglobin A (HbA) is not acid resistant. When a fixed blood smear is dipped in acid buffer, the adult erythrocytes lose the haemoglobin A in the buffer and only retain their stroma while the foetal erythrocytes remain intact. Therefore the fetal erythrocytes after HemaFetal staining appear pink-red or pink, while the maternal erythrocytes appear as colorless “ghosts”. The percentage of fetal red blood cells in maternal blood is used to calculate the volume of fetomaternal bleeding.
The Hemafix® -staining solutions are ready-to-use and standardized. They provide a reproducible and constant staining quality. Filtration is not necessary. Sedimentation of undissolved colour particles does not take place. A standardized performance of the Kleihauer-Betke test with low time and cost expenditure can be achieved by using an automatic stainer.