Haematology and Blood Banking
What this domain tests
This section covers blood counts, anticoagulants, coagulation tests and safe transfusion practice: ABO/Rh grouping, crossmatching, storage and recognition of transfusion reactions.
Core rules
- EDTA is the anticoagulant for CBC; citrate is for PT/INR and APTT. Fill citrate to the correct line because excess or short volume changes the ratio.
- Report Hb, PCV, RBC count, MCV, MCH, MCHC, total and differential WBC, and platelet count. Examine a peripheral smear for red-cell shape, inclusions and WBC morphology.
- ABO grouping uses anti-A, anti-B and anti-D sera; reverse grouping uses known A and B cells. Crossmatch confirms donor-recipient compatibility.
- Store red cells at 2-6°C, platelets at 20-24°C with agitation, and fresh frozen plasma at -30°C or colder.
- A transfusion reaction may present with fever, chills, urticaria, dyspnea, back pain or dark urine. Stop the transfusion, maintain IV access, and report immediately.
Worked example
An unconscious trauma patient needs blood before grouping is complete. Reasoning: group O RhD-negative red cells are the safest emergency choice because they lack A, B and D antigens. Switch to ABO/Rh-specific blood as soon as the group is confirmed.
Traps
- Using EDTA blood for coagulation tests.
- Assuming RhD-positive blood is safe for a woman of childbearing age.
- Shaking red cells or freezing them.
- Continuing a transfusion when a reaction is suspected.