Autoimmune Hemolytic Antibody Screen (Direct Coombs Test)

What This Test Measures

The test detects the presence of antibodies (specifically IgG or IgM) that bind to red blood cells. These antibodies can trigger the immune system to mistakenly destroy your red blood cells, leading to conditions like autoimmune hemolytic anemia. The test uses a direct method to identify these antibodies on your red blood cells, rather than measuring their presence in the plasma alone.

Why It’s Done

Your healthcare provider may order this test if you have symptoms like fatigue, pale skin, shortness of breath, or unexplained anemia. It’s also used during blood transfusions to ensure compatibility or in cases where you’ve been exposed to certain medications or conditions that may trigger autoimmune reactions.

Sample Collection and Preparation

A small sample of your blood is drawn from a vein, usually in your arm. The blood is then processed in the lab to separate red blood cells from plasma. The red blood cells are mixed with a reagent containing antibodies specific to human red blood cells (Coombs reagent). If antibodies are present, they will bind to your red blood cells, making them more susceptible to destruction.

What to Expect Before the Test

There are no special preparations needed for this test. However, inform your healthcare provider about any medications you’re taking, especially blood thinners or recent vaccinations, as they may affect results.