Coombs Test, Direct
The Coombs test, direct is a diagnostic tool used to identify a form of anaemia triggered by immune system dysfunction. Your immune system works to defend your body and produces antibodies to combat foreign agents. However, in certain instances, it can produce antibodies targeting red blood cells, vital for oxygen transport throughout the body. Consequently, these antibodies cause the premature breakdown of red blood cells, leading to a condition known as haemolytic anaemia.
The Coombs test, direct helps clinicians detect the presence of such antibodies bound to red blood cells and aids in diagnosing and managing this condition. Thus, getting this test done is recommended to diagnose haemolytic anaemia.
Symptoms of haemolytic anaemia
Tiredness
Shortness of breath
Headaches or dizziness
Paleness of skin
Jaundice (yellowing of skin, eyes, or under your tongue)
Dark urine
Heart problems, such as an irregular heartbeat
Low numbers of red blood cells
Enlarged liver or spleen
Swelling of the body (legs, abdomen)
Who should get tested?
Coombs test, direct is recommended for the following individuals and conditions:
Individuals with symptoms of hemolytic anemia
Individuals who have had a blood transfusion recently and are experiencing symptoms of a transfusion reaction
Newborn with symptoms of a haemolytic disease of the newborn
Preparation for the test
No special preparation is required for the Coombs test, direct.
Interpretation of the test results
The test results are available as positive or negative.
Positive
A positive (abnormal) result from a Coombs test, direct suggests the presence of antibodies targeting your red blood cells. This could indicate various conditions such as:
- Autoimmune haemolytic anaemia
- Chronic lymphocytic leukemia or similar disorders
- Erythroblastosis fetalis (haemolytic disease of the newborn)
- Infectious mononucleosis
- Mycoplasma infection
- Syphilis
- Systemic lupus erythematosus (SLE)
- Transfusion reactions, often caused by improperly matched units of blood
Negative
A negative (normal) result from a Coombs test, direct indicates a negative finding, indicating the absence of cell clumping and no presence of antibodies against red blood cells. Note: The interpretation of normal values may vary slightly across different laboratories due to differences in measurement techniques or sample types. It is advised to discuss your specific test results with your healthcare provider.
FAQs
How is the Coombs test, direct performed?
Coombs test, direct involves collecting a small sample of blood from the patient via venipuncture, typically from a vein in the arm. The collected blood is then centrifuged to separate the red blood cells from the serum. Next, the red blood cells are washed to remove any unbound antibodies or complement proteins. Finally, the washed red blood cells are mixed with an anti-human globulin reagent to detect any antibodies bound to the patient's red blood cells.
What are the risks associated with the Coombs test, direct?
There are no known risks associated with this test. During a blood test, one may experience minor pain or bruising where the needle was inserted, but most symptoms will subside quickly.
What is the turnaround time (TAT) of the Coombs test, direct?
The test results are usually available within the same working day as the sample collection. This duration may vary depending on the diagnostic clinic.
What are the various causes of haemolytic anaemia?
Haemolytic anaemia can result from various factors including autoimmune disorders where the body attacks its own red blood cells, inherited conditions such as sickle cell disease or thalassemia, infections such as malaria or certain bacteria, exposure to toxins or drugs, mechanical factors such as blood vessel abnormalities or artificial heart valves. Each cause disrupts red blood cell production or function, leading to their premature destruction.
Can I get antibodies from donating blood?
When donating blood, you won't be exposed to anyone else's blood, so you won't receive antibodies from donating blood.
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