Final answer:
The direct antiglobulin (direct Coombs') test is used to detect autoimmune disorders where antibodies are produced against one's own red blood cells. It can identify hemolytic diseases in newborns, diagnose autoimmune responses, and determine the cause of jaundice in infants.
Step-by-step explanation:
The direct antiglobulin (direct Coombs') test is designed to detect when people have a disease that results in the production of antibodies that bind to their own red blood cells, causing an immune response against the cells. Notably, this test is used to diagnose autoimmune disorders that involve such self-directed antibodies. Conditions that may result in a positive direct Coombs' test include autoimmune hemolytic anemia, hemolytic transfusion reactions, some infections like Epstein-Barr virus and Mycoplasma pneumonia, certain types of cancer, and allergic reactions to drugs like penicillin.
When a baby is born with jaundice, indicating excessively high levels of bilirubin due to red blood cell breakdown, the direct Coombs' test can determine if this is caused by the mother's antibodies attacking the baby's red blood cells. The indirect Coombs' test, or indirect antiglobulin test (IAT), on the other hand, screens for unbound antibodies against red blood cell antigens in a patient's serum and is typically used prior to blood transfusions and to screen pregnant women for antibodies that might cause hemolytic disease of the newborn.