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
- Assess for latex allergy.
- Assess for bleeding disorders.
- Note any medication or supplement taken by the patient that may cause excessive bleeding.
During the procedure
- The nurse selects a vein that will be used in the test. In most cases, the vein in the arm is usually selected.
- A tourniquet (large rubber strap) is secured above the selected vein.
- The skin over the vein is cleaned, and a needle will be inserted.
- Instruct the client to hold very still while the blood is collected.
- After blood is collected into one or more tubes, the tourniquet is removed.
- 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”).
- 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
- A bandage, cotton ball or gauze is placed on the area where the needle was inserted.
- Apply pressure to the area.
- Strenuous exercises should be avoided after the test is done.
- Pain, redness, swelling or discharges from the puncture site should be reported to the physician immediately.