Which of the following test is done to differentiate between maternal and fetal blood in a case of fetomaternal hemorrhage?

Kleihauer - Betke test is an acid elution test used to detect fetal RBC in maternal circulation. This test gives a percentage of fetal RBC in maternal circulation and helps in estimating the extend of feto maternal hemorrhage. Fetal RBC contain HbF which is more resistant to acid elution than HbA. After exposure to acid only fetal Hb remains. Fetal red cells can then be identified by uptake of a special stain and quantified on peripheral smear.