Kleihauer Betke Test (Fetal Erythrocytes) Test

The Kleihauer-Betke test is performed to determine the degree of fetal-maternal hemorrhage (FMH) and to help calculate the dosage of Rh immune globulin to be given in some cases of Rh-negative mothers. A test to identify fetal red blood cells in the maternal circulation, an abnormal finding identified when fetomaternal hemorrhage has occurred. Fetomaternal hemorrhage (FMH) is the breakage of the placental barrier, allowing fetal hemoglobin to get mixed with maternal blood. In response to this, maternal immune system gets activated, and isoimmunization may occur if the mother is Rhesus-D protein negative and the fetus is RhD positive. The maternal antibodies bind to the fetal +ve erythrocytes, leading to hemolysis, anemia, hydrops fetalis and possible fetal death.

Specimen Collection: Blood Sample is collected The blood is immediately transferred into the blood container containing appropriate preservatives or clot activator or anti-coagulant. Patient Preparation: No special preparation is needed prior to the test.

Administration of RhIG inhibits formation of Rh antibodies in the mother to prevent Rh disease in future pregnancies with Rh-positive children. The test is also used to resolve the question of whether FMH was the cause of fetal death in the case of stillbirth.

The KB test is the standard method of quantitating fetal-maternal hemorrhage (FMH). It takes advantage of the differential resistance of fetal hemoglobin to acid. A standard blood smear is prepared from the mother's blood, and exposed to an acid bath. The Kleihauer-Betke Blood Test detects fetal red blood cells in a pregnant woman or a woman who has recently delivered. It is performed as follows: The mother’s blood is treated with acid, which destroys the acid-sensitive maternal hemoglobin (a protein abundant in red blood cells) while leaving fetal acid-resistant hemoglobin intact A stain is added to expose the infant hemoglobin The number of fetal red blood cells are counted, then divided by the number of maternal red blood cells, and the result is divided by 10,000 and expressed as fetal bleed (in milliliters) NOTE: If ongoing and rapid hemorrhages are occurring then immediate delivery of the foetus may be indicated if the fetus is sufficiently developed. If the hemorrhages has already occurred and now stopped, an inutero transfusion of red cells to the foetus may be recommended.