Determination of ABO and Rh blood groups together with testing of compatibility (crossmatch) between recipient and donor blood. Performed before transfusion and surgery.
Indication
- Preparation before planned or emergency surgery
- Compatibility assessment before blood product transfusion (red cells, plasma, platelets)
- Planning blood replacement due to anemia or bleeding
- Prenatal workup and screening for Rh incompatibility
- Evaluation of newborn jaundice (hemolytic disease)
- Preparation for organ or bone marrow transplantation
- Alloantibody screening in patients receiving repeated transfusions
Preparation
- No special patient preparation is generally required
- Patient identification is double-checked when labeling the tube (mislabeled samples are a major risk)
- Any history of previous transfusion or pregnancy must be reported to the laboratory
- In emergencies, the sample is delivered to the laboratory as quickly as possible
- Current medications and recent blood products should be reported to the physician
How it's performed
- About 3-6 mL of venous blood is drawn into an EDTA tube
- ABO grouping (A, B, AB, O) is determined by both forward and reverse methods
- The Rh (D) antigen is assessed in a separate tube
- The patient's serum is screened for alloantibodies using the indirect antiglobulin (Coombs) test
- Compatibility between donor blood and recipient serum is confirmed by major crossmatch
- The compatible blood product is approved and labeled for transfusion
Post-procedure
- Emergency crossmatch results in approximately 30-60 minutes; full Coombs screening may take 60-90 minutes
- The patient is closely monitored during the first 15 minutes of transfusion
- Symptoms such as fever, chills, or change in urine color should be reported to the physician
- Compatibility testing is repeated with a new sample for each subsequent transfusion
- Results are stored in the transfusion service records together with the patient file
Risks
- Bruising or mild pain at the venipuncture site
- Serious transfusion errors if samples are mislabeled (which is why double-check identification is mandatory)
- Delays in finding compatible blood when rare alloantibodies are present
- Very rare false positive or false negative results due to laboratory error
FAQ
Can my blood group change during my lifetime?
No. ABO and Rh blood groups are inherited at birth and do not change. Temporary differences may be seen after some bone marrow transplantations.
Why is the crossmatch test needed?
Even within the same blood group, each person's serum may contain small antibody differences. Crossmatch is required to prevent transfusion reactions.
How long does the result take?
In emergency situations, compatibility may be released within 30-60 minutes; broader antibody screening can take longer.
What does being Rh negative mean?
It means your red blood cells lack the Rh-D antigen. It requires special follow-up during pregnancy and transfusion but is not a disease.
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