Antiglobulin test is formally known as Direct Antiglobulin Test. You may hear doctors or nurses use words such as DAT, Direct Coomb’s test or direct anti-human Globulin test – these are all similar terms used in the health care setting.
Antiglobulin test came into its existence for the purpose of the following:
- Diagnosis of hemolytic anemia which is either due to autoimmune disease or drug-induced reaction – antibodies sometimes does not recognize RBC antigens and take it as a foreign body. This is the tendency when the defense is turned within itself (auto means self) in the immune system causing self-destruction instead of defending the body.
- Blood transfusion reaction – This test is very important for cases that massive blood transfusion is being done. Though it is a standard operating procedure to cross match the donor’s blood type with the patient’s blood type, sometimes the body would create antibodies and attach to the transfused blood.
- Diagnosis of hemolytic anomalies in the newborn – The newborn’s blood is being tested whether the mother’s antibodies have gone within the infant’s red blood cells. If this happens, this means that there is a tendency that the mother’s antibodies will take the red blood cells of the newborn as enemies and attack it. The rapid destruction of red blood cells may be manifested with yellowish skin and on sclera of the baby. This case is common when the father and mother has different blood type.
The focus of this test is the antigens that are attached in the Red Blood Cells. There are two antigens called Group A and Group B. Genetically, group A and group B antigens gets a copy of it from their parents. Aside from that the two major surface antigen, each antigen is also grouped through Rh (+) positive or Rh (-) negative. This means that if the blood has Type A (+) positive, the antigen in the blood is Type A with a Rh antigen also. Negative or positive sign means the absence or presence of Rh group.
Interpretation of the result:
- Positive – This means that there is presence of antibodies in the red blood cells. Physical manifestations may support this result. The positive result may last within 24 hours to 3 months for infections, transfusion reactions. While for autoimmune diseases, it may last more than that.
- Negative – having a negative result means that the antibodies have not reached the red blood cells. Physical manifestations of the reaction may have different cause.