From the Guidelines
The Coombs test should be checked within 72 hours after a blood transfusion, and ideally as soon as possible if a transfusion reaction is suspected, as stated in the association of anaesthetists guidelines: the use of blood components and their alternatives 1. When checking the Coombs test after transfusion, it is essential to consider the patient's history of blood transfusion or pregnancy within the previous 3 months, as this may affect the validity of the sample 1. Some key points to consider when checking the Coombs test include:
- The test detects antibodies bound to red blood cells, which can indicate an immune response to the transfused blood
- Delayed hemolytic transfusion reactions can occur days after a transfusion when the recipient's immune system produces antibodies against the donor's red blood cells
- The Coombs test helps identify this process before severe hemolysis occurs
- If a patient develops symptoms like fever, jaundice, or unexplained decrease in hemoglobin after transfusion, the test should be performed immediately regardless of timing
- Blood samples for the test should be collected before any additional transfusions are given to avoid confounding results It is also crucial to follow proper patient identification procedures to minimize wrong-blood-in-tube events and risks of ABO incompatibility, as emphasized in the guidelines 1. In situations where the patient's identity may be unknown, an alternative identification system must be in place, and once the patient's identity is known, a new identification band must be attached to the patient, and a new transfusion sample must be collected and labelled with the patient's details 1.
From the Research
Coombs Test After Transfusion
The Coombs test, also known as the direct antiglobulin test, is a crucial laboratory test used to diagnose hemolytic transfusion reactions.
- The test can be performed immediately after a transfusion reaction is suspected, as it can help identify whether the reaction is due to an immune response against the transfused blood cells 2.
- In some cases, the direct Coombs test may be negative immediately after transfusion, but it can become positive several days later, making it essential to repeat the test if a hemolytic reaction is suspected 3.
- The Coombs test is usually ordered when hemolytic anemia is suspected or if a transfusion reaction has occurred, and it can help increase understanding of what is measured and why it is ordered 4.
Timing of Coombs Test
- There is no specific time frame for when the Coombs test should be performed after transfusion, but it is generally recommended to perform the test as soon as possible after a transfusion reaction is suspected 2, 3.
- In some cases, the test may need to be repeated several days after the transfusion to confirm the diagnosis of a hemolytic reaction 3.
- The timing of the Coombs test may also depend on the clinical presentation and the severity of the transfusion reaction, as well as the patient's medical history and current treatment 5.