Kleihauer-Betke (KB) Test

The Kleihauer-Betke (KB) test is a blood test that measures the amount of fetal hemoglobin transferred from a fetus to the mother’s bloodstream. It is usually done for the purpose of determining the RhoGam dose. This test is used to predict certain types of pregnancy complications, particularly after a mother has suffered a traumatic injury. Kleihauer-Betke Test is usually performed on Rhesus-negative mothers to determine the required dose of Rho (D) Immnuglobulin (RhIg) to inhibit the formation of Rh antibodies in the mother and prevent Rh disease in future Rh-positive children.
Other Names of Kleihauer-Betke Test

• Fetal RBC determination
• Fetomaternal haemorrhage calculation, Kleihauer-Betke method
• Fetomaternal hemorrhage calculation, Kleihauer-Betke method
• Haemoglobin F cytochemical demonstration test
• Hemoglobin F cytochemical demonstration test

Purpose of Kleihauer Betke Test:

• Complication related to pregnancy. This test is used to predict certain types of pregnancy complications, particularly after a mother has suffered a traumatic injury.
• Measures fetal cells in maternal circulation. Staining of postpartum maternal blood for identification of percentage of fetal cells present
• Used in assessing for Rh Sensitization ( Maternal blood Rh negative, Large antepartum bleed)
• Determine possible fetal maternal hemorrhage in the newborn, aid in diagnosis of certain types of anemia in adults; assess the magnitude of fetal maternal hemorrhage; calculate dosage of Rh immune globulin to be given.

Normal Range or Value
Full-term newborns: Hb F cells are > 90%; normal adults Hb F cells are < 0.01%.
Before the Procedure

1. Assess for latex allergy.
2. Assess for bleeding disorders.
3. Note any medication or supplement taken by the patient that may cause excessive bleeding.

During the procedure

1. The nurse selects a vein that will be used in the test. In most cases, the vein in the arm is usually selected.
2. A tourniquet (large rubber strap) is secured above the selected vein.
3. The skin over the vein is cleaned, and a needle will be inserted.
4. Instruct the client to hold very still while the blood is collected.
5. After blood is collected into one or more tubes, the tourniquet is removed.
6. Expose blood smear to acid bath (this removes adult hemoglobin, which is acid-sensitive) but not fetal hemoglobin. Stain smear (fetal cells appear pink; maternal cells look like “ghosts”).
7. Count lots of cells and report percentage of cells that are fetal (specifically: you count the number of fetal blood cells per 50 low power fields. If you see 5 cells per 50 low power fields, that’s equivalent to a 0.5 mL fetomaternal hemorrhage).

After the Procedure

1. A bandage, cotton ball or gauze is placed on the area where the needle was inserted.
2. Apply pressure to the area.
3. Strenuous exercises should be avoided after the test is done.
4. Pain, redness, swelling or discharges from the puncture site should be reported to the physician immediately.