The Kleihauer-Betke (KB) test is an important blood test used during pregnancy to detect fetal red blood cells in the maternal circulation, mainly to assess the severity of fetomaternal hemorrhage (FMH). FMH occurs when fetal blood enters the maternal circulation due to trauma, complications during pregnancy, or invasive prenatal procedures. The test is especially useful for Rh-negative individuals, who may develop anti-Rh antibodies when Rh-positive fetal blood enters their circulation. Anti-Rh immune globulin is given to Rh-negative individuals to prevent the formation of these antibodies, and the KB test helps quantify the amount of fetal blood in the maternal circulation to determine the appropriate dose of immune globulin.
The KB test works by distinguishing between fetal and maternal blood cells based on the type of hemoglobin that is present. Fetal hemoglobin is more resistant to acid elution than adult hemoglobin, which is used to wash away maternal hemoglobin from the sample. The fetal hemoglobin remains intact, and the fetal cells are stained and counted to estimate the total volume of fetal blood. A positive KB test indicates the presence of fetal blood in the maternal circulation, and the total amount of fetal blood is reported rather than a simple positive or negative result. The sensitivity of the test is 5 mL, which means that FMH of less than 5 mL may not be detected.
In conclusion, the Kleihauer-Betke test is a quantitative blood test used during pregnancy to detect fetal red blood cells in the maternal circulation. It is most commonly used to assess the severity of fetomaternal hemorrhage, especially for Rh-negative individuals who may develop anti-Rh antibodies in response to Rh-positive fetal blood. The test helps determine the appropriate dose of anti-Rh immune globulin to prevent the formation of these antibodies, and the sensitivity of the test is 5 mL. The KB test is an important tool for managing the health of both the pregnant individual and the fetus, and it is an essential part of prenatal care.