Final answer:
The Coombs' test, which includes both direct and indirect variations, is used to diagnose immune hemolytic anemia, identifying antibodies that cause the destruction of red blood cells.
Step-by-step explanation:
The test used to diagnose immune hemolytic anemia is called the Coombs' test. There are two types of Coombs' tests: the direct Coombs' test (DAT) and the indirect Coombs' test (IAT). The DAT is used to detect antibodies or complement proteins that are bound to red blood cells in vivo, which is a key indicator of hemolytic anemia, while the IAT screens for unbound antibodies against red blood cell antigens in vitro.
To perform a DAT, a blood sample is taken from a patient that might have hemolytic anemia. A few drops of Coombs' reagent, which contains antibodies against human immunoglobulins, is then mixed with the patient's blood sample. If the reagent causes agglutination of red blood cells, it indicates the presence of nonagglutinating antibodies or complement, supporting a diagnosis of hemolytic anemia.
The IAT is especially useful in blood transfusion preparations and screening pregnant women for antibodies that might cause hemolytic disease in newborns. Both these tests are critical for diagnosing conditions that lead to the destruction of red blood cells.