Which laboratory test on a post-transfusion specimen helps confirm immune involvement in a suspected transfusion reaction?

Which laboratory test on a post-transfusion specimen helps confirm immune involvement in a suspected transfusion reaction?

• A. Direct antiglobulin test
• B. Indirect antiglobulin test
• C. Hematocrit
• D. Platelet count

Answer: (A)

The test used to confirm immune involvement in a suspected transfusion reaction is the direct antiglobulin test. This assay is performed on the patient’s post-transfusion red cells to see if antibodies (usually IgG) or complement components are already bound to the red cells in vivo. If the direct antiglobulin test is positive, it indicates that immune-mediated hemolysis is occurring as part of the transfusion reaction, because the patient’s red cells are being targeted by immune factors. The indirect antiglobulin test, by contrast, looks for free antibodies in the patient’s serum that could react with donor red cells, and it’s typically used for pretransfusion antibody screening rather than confirming an ongoing post-transfusion, immune-mediated process. Hematocrit is a measure of the proportion of red blood cells in blood and can reflect the degree of hemolysis or blood loss, but it doesn’t by itself show that the reaction is immune in nature. Platelet count relates to platelet status and transfusion reactions involving platelets, but it’s not a direct indicator of immune-mediated red cell destruction.

The test used to confirm immune involvement in a suspected transfusion reaction is the direct antiglobulin test. This assay is performed on the patient’s post-transfusion red cells to see if antibodies (usually IgG) or complement components are already bound to the red cells in vivo. If the direct antiglobulin test is positive, it indicates that immune-mediated hemolysis is occurring as part of the transfusion reaction, because the patient’s red cells are being targeted by immune factors.

The indirect antiglobulin test, by contrast, looks for free antibodies in the patient’s serum that could react with donor red cells, and it’s typically used for pretransfusion antibody screening rather than confirming an ongoing post-transfusion, immune-mediated process. Hematocrit is a measure of the proportion of red blood cells in blood and can reflect the degree of hemolysis or blood loss, but it doesn’t by itself show that the reaction is immune in nature. Platelet count relates to platelet status and transfusion reactions involving platelets, but it’s not a direct indicator of immune-mediated red cell destruction.