Final answer:
The Kleihauer-Betke (KB) test is a screening test for fetal-maternal hemorrhage, used to detect fetal hemoglobin in maternal blood, especially after trauma or to determine Rh immunoglobulin dosage.
Step-by-step explanation:
The Kleihauer-Betke (KB) test is B. a screening test for fetal-maternal hemorrhage. This laboratory test is utilized to detect the presence of fetal hemoglobin in maternal blood. It is most often used after events of trauma, suspected placental abruption, or to determine the appropriate dosage of Rh immunoglobulin in Rh-negative mothers to prevent Rh disease in future pregnancies. During the KB test, maternal blood smear is treated with an acid solution that denatures adult hemoglobin but leaves fetal hemoglobin intact, which is then stained and quantified under a microscope. The difference in resistance to acid helps in distinguishing between fetal and maternal red blood cells.