Direct Coombs Test (DCT)
Test Description
The Direct Coombs Test (DCT), also referred to as the Direct Antiglobulin Test (DAT), is a diagnostic blood test used to detect autoimmune hemolysis—a condition where antibodies or complement proteins are attached to red blood cells (RBCs), marking them for premature destruction by the immune system.
This immune reaction can lead to hemolytic anemia, a potentially serious condition characterized by fatigue, pallor, shortness of breath, and jaundice. The DCT plays a vital role in both diagnosing and managing patients with immune-related blood disorders.
Indications of the Direct Coombs Test (DCT)
The direct Coombs test is required in these scenarios:
- Autoimmune Hemolytic Anemia (AIHA): To confirm immune-mediated destruction of red blood cells.
- Hemolytic Disease of the Newborn (Erythroblastosis Fetalis): To detect maternal antibodies attached to fetal RBCs.
- Chronic Lymphocytic Leukemia (CLL): Used to assess for secondary hemolysis in hematologic malignancies.
- Systemic Lupus Erythematosus (SLE): Helps monitor immune-related damage to blood components.
- Infectious Triggers: Such as Mycoplasma pneumoniae or Epstein-Barr virus, which may cause cold agglutinin hemolysis.
- Drug-Induced Hemolysis: Identifies antibodies formed in response to certain medications.
Patient Preparation/Instructions
Preparation:
- No fasting or special preparation is required before the test.
Instructions for Patients:
- Inform your doctor about any recent transfusions, ongoing infections, or current medications, as these factors can affect results.
- A simple blood sample will be drawn from a vein, usually in the arm.
- Some patients may experience mild bruising or discomfort at the site of venipuncture.
Test Procedure
1. Sample Collection:
- Blood is collected in an EDTA tube to prevent clotting.
2. Red Blood Cell Preparation:
- The sample is centrifuged to separate red blood cells from plasma.
- RBCs are washed multiple times with saline to remove unbound antibodies.
3. Testing:
- The washed RBCs are suspended in a saline solution to make a 3–5% cell suspension.
- Coombs reagent (antihuman globulin) is added to the sample.
- The test tube is gently centrifuged.
4. Observation:
- The sample is visually examined for agglutination, or clumping of red cells.
Interpretation of Results
- Positive Result: Agglutination is present. Indicates that antibodies or complement proteins are attached to the patient’s red blood cells, confirming immune-mediated hemolysis.
- Negative Result: No agglutination is observed. Suggests no immune coating is present on RBCs and helps rule out immune-related hemolytic processes.
Typical Reference Values
- Negative: No visible agglutination—normal finding.
- Positive: Agglutination present—abnormal; suggests autoimmune or alloimmune hemolysis.
Turnaround Time
Results from the direct Coombs test are usually available within a few hours to one day, depending on the laboratory’s processing capabilities. In emergency or inpatient settings, results may be expedited.
How To Order Direct Coombs Test
Please click the ‘Order Test’ button and put the Direct Coombs Test in your cart.
You are welcome to visit our laboratory in Kilimani, Nairobi. This will initiate the process for obtaining your test
