Kleihauer test, The Kleihauer test, also known as the Kleihauer-Betke test, is a medical test used to determine the amount of fetal hemoglobin (HbF) in a pregnant woman’s bloodstream. This test is primarily performed in situations where there is a risk of fetal-maternal hemorrhage, such as trauma during pregnancy, placental abruption, or other conditions that could lead to the mixing of maternal and fetal blood.
The test is named after Dr. Theodore Kleihauer and Dr. Herbert Betke, who developed it in the 1950s. It is a valuable tool for assessing the extent of fetal blood loss into the maternal circulation, which is essential for determining the appropriate dosage of Rh immune globulin (RhoGAM) in Rh-negative mothers. RhoGAM is administered to Rh-negative women to prevent sensitization to Rh-positive blood, which could affect future pregnancies.
Here’s how the Kleihauer test works:
- Blood Sample: A sample of the pregnant woman’s blood is collected, typically from a vein in her arm.
- Staining: The blood sample is treated with a special stain that highlights fetal hemoglobin. Fetal hemoglobin differs from adult hemoglobin, and the stain helps distinguish between the two.
- Microscopy: A laboratory technician examines the stained blood sample under a microscope. They count the number of fetal red blood cells (RBCs) and maternal RBCs.
- Calculation: Based on the number of fetal RBCs counted, the technician calculates the percentage of fetal hemoglobin in the maternal circulation. This information is used to determine the amount of RhoGAM that needs to be administered to prevent sensitization.
What is a positive Kleihauer-Betke test?
A positive Kleihauer-Betke test, also known as a Kleihauer-Betke stain or Kleihauer test, is a medical test used to determine the amount of fetal hemoglobin (HbF) that has entered the maternal bloodstream. This test is typically performed on pregnant individuals, especially after trauma or certain medical procedures, to assess the risk of fetal blood mixing with the maternal circulation.
During pregnancy, there can be instances where fetal blood enters the maternal circulation, which can be concerning if the mother is Rh-negative and the fetus is Rh-positive. This mixing of blood can lead to sensitization of the mother’s immune system to the Rh antigen, potentially causing hemolytic disease of the newborn (HDN) in subsequent pregnancies.
A positive Kleihauer-Betke test indicates that fetal hemoglobin has indeed entered the maternal bloodstream. The test involves staining maternal blood with a special dye that binds to fetal hemoglobin. Technicians then examine the blood sample under a microscope to count the number of fetal red blood cells (RBCs) relative to maternal RBCs. The results are expressed as a percentage of fetal RBCs in the maternal circulation.
Depending on the percentage of fetal RBCs found in the maternal circulation, healthcare providers can assess the risk of sensitization and determine if Rh immune globulin (RhIg) should be administered to prevent maternal sensitization in cases where the mother is Rh-negative and the fetus is Rh-positive.
In summary, a positive Kleihauer-Betke test indicates that fetal blood has entered the maternal circulation, which may have implications for the management of Rh incompatibility during pregnancy.
What are the most important facts to know about the Kleihauer-Betke test?
This test is typically performed when there is a concern about fetal-maternal hemorrhage, such as in cases of trauma or certain medical conditions. Here are some important facts to know about the Kleihauer-Betke test:
- Purpose: The primary purpose of the KB test is to quantify the amount of fetal hemoglobin in the maternal circulation. This information is essential in cases where there is a risk of fetal-maternal hemorrhage, which can occur during childbirth, trauma, or other situations.
- Fetal Hemoglobin (HbF): Fetal hemoglobin is a type of hemoglobin that is found in the blood of developing fetuses. It differs from adult hemoglobin (HbA) and is typically present in smaller amounts in the maternal bloodstream. An increase in fetal hemoglobin in the maternal circulation suggests fetal-maternal hemorrhage.
- Rh Incompatibility: The KB test is commonly used in cases of Rh (Rhesus) incompatibility, where a Rh-negative mother is carrying a Rh-positive fetus. If fetal blood enters the maternal circulation, it can sensitize the mother’s immune system, leading to potential complications in subsequent pregnancies.
- Testing Method: The KB test involves staining a blood smear with a special dye called acid elution stain. This stain distinguishes between fetal and adult hemoglobin. Fetal hemoglobin (HbF) stains differently from adult hemoglobin (HbA), making it possible to count the fetal cells.
- Calculation: After staining, a microscope is used to count the number of fetal red blood cells (fetal cells) and adult red blood cells (maternal cells) in the smear. The ratio of fetal cells to total cells is used to estimate the percentage of fetal hemoglobin in the maternal bloodstream.
- Threshold: There is typically a threshold level (e.g., 1%) above which intervention may be required, such as administering Rh immunoglobulin (RhIg) to prevent Rh sensitization in Rh-negative mothers carrying Rh-positive fetuses.
- Timing: The KB test can be performed after any event or situation where fetal-maternal hemorrhage is suspected, such as trauma, amniocentesis, chorionic villus sampling (CVS), or delivery. It is essential to perform the test as soon as possible after the event to accurately assess the extent of hemorrhage.
- Clinical Importance: The KB test is crucial for determining the need for RhIg administration in cases of Rh incompatibility. If a significant fetal-maternal hemorrhage is detected, RhIg can help prevent the mother from developing Rh antibodies that could harm future pregnancies.
- Interpretation: Results of the KB test guide medical decisions, and healthcare providers use the findings to determine the appropriate treatment or management for the mother and fetus.
- Monitoring: In some cases, serial KB tests may be required to monitor the clearance of fetal cells from the maternal circulation over time.
It’s important to note that the KB test is just one component of the comprehensive care provided during pregnancy and in situations where fetal-maternal hemorrhage is a concern. Healthcare professionals will use the results of this test in conjunction with clinical judgment to make appropriate recommendations and decisions for the patient’s care.