MLT GlobeBlood Banking: Crossmatch & compatibility
51 Blood Banking MCQs on Crossmatch & compatibility with answers and explanations.
A patient is group O, RhD-negative. Which red cell unit is fully compatible?
Group O plasma has anti-A and anti-B, so only group O cells are ABO-compatible. An RhD-negative recipient should receive RhD-negative cells to avoid anti-D sensitisation.
In an emergency when the recipient's group is unknown, red cells of which ABO/RhD group are given?
O RhD-negative red cells lack A, B and D antigens, so they are not destroyed by recipient anti-A, anti-B or anti-D. AB patients are the universal plasma donors instead.
In a minor crossmatch, which two components are tested together?
The minor crossmatch looks for donor antibodies against the patient's cells. The major crossmatch (recipient plasma + donor cells) is the one routinely performed.
Testing recipient serum against donor red cells is called the:
The major crossmatch detects recipient antibodies that would destroy transfused donor cells, the most dangerous incompatibility.
An O RhD-negative patient needs red cells. Which donor units are compatible?
Group O plasma contains anti-A and anti-B, so only O cells are compatible, and D-negative cells prevent anti-D formation.
A group B patient needs plasma. Which plasma groups are ABO-compatible?
Plasma must lack antibodies to the recipient's antigens. Group B plasma (anti-A) and AB plasma (no antibodies) are safe; group O plasma contains anti-B.
A group A, D-negative woman aged 25 needs red cells. Which units are the correct choice?
Group A patients have anti-B, so A or O red cells are compatible. D-negative units prevent anti-D formation in a woman of childbearing potential.
Blood is released before pretransfusion testing is complete. Which record is required?
Emergency release requires the requesting physician to document that the clinical situation justified transfusion before testing was finished. Testing is completed afterwards and abnormalities reported at once.
A trauma patient of unknown blood group needs plasma immediately. Which plasma group is the universal choice?
AB plasma contains neither anti-A nor anti-B, so it is compatible with every ABO group. Group O plasma contains both antibodies.
Massive transfusion in an adult is commonly defined as:
Massive transfusion is replacement of about one total blood volume (roughly 10 or more red cell units in an adult) within 24 hours.
After transfusion, the patient's pretransfusion sample and a donor segment must be kept refrigerated for at least:
Keeping both samples for at least 7 days allows re-testing if a delayed or acute reaction is investigated.
Which information is required on the label of a pretransfusion blood sample tube?
The tube must carry two independent identifiers (such as full name and unique ID number) and the collection date, and the phlebotomist must be identifiable. Unlabeled or mislabeled samples are rejected.
The minor crossmatch, no longer routinely performed, tests:
The minor crossmatch detects donor antibodies against the patient's red cells. It was dropped because donor plasma is screened for unexpected antibodies.
At the time of issue from the blood bank, which check is required?
Before issue, staff verify the recipient's identification, the unit number, ABO/D groups, compatibility, expiry date, and inspect the unit visually. Retesting is not required.
At the bedside, just before transfusion begins, the most important check is:
Most fatal ABO reactions are caused by giving the right unit to the wrong patient. Two identifiers on the wristband must match the unit's compatibility label before starting.
A crossmatch is considered compatible when:
Compatible means no agglutination and no hemolysis at any phase tested. Hemolysis counts as a positive (incompatible) reaction.
A 'type and screen' request means the laboratory performs:
In a type and screen, the patient is grouped and screened. Units are crossmatched only if transfusion becomes likely, which saves blood inventory.
Donor red cells for crossmatching are usually taken from:
Segments attached to the bag contain the same donor blood and can be removed without opening the unit.
Before a pretransfusion blood sample is collected, the patient must be identified using at least:
Positive patient identification with at least two identifiers prevents wrong-blood-in-tube errors. Bed numbers are never acceptable identifiers.
Once started, a unit of red cells should be completely transfused within:
Red cells should be infused within 4 hours of spiking the bag to limit bacterial growth at room temperature.