The Kleihauer-Betke ("KB") test, Kleihauer-Betke ("KB") stain or Kleihauer test, is a bloo test used to measure the amount of fetal hemoglobin transferred from a fetus to an Rh-negative mother's bloodstream. The results of the test are used to determine the required dose of Rh immune globulin (RhIg) to inhibit formation of Rh antibodies in the mother and prevent Rh disease in future Rh-positive children.