MLPAO Transfusion Medicine Fundamentals Flashcards
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What is the maximum time a unit of red blood cells can be out of the blood bank refrigerator before it must be transfused or discarded?
Answer: 30 minutes (the '30-minute rule')
According to Canadian Blood Services guidelines, red blood cell units must be returned to controlled storage within 30 minutes of issue if not being transfused. Once a unit has been out of the blood bank refrigerator (1-6°C) for more than 30 minutes and has not been initiated, it cannot be returned to inventory and must be discarded.
Which antibodies are considered clinically significant in transfusion medicine?
Answer: IgG antibodies reactive at 37°C that can cause hemolytic transfusion reactions or HDFN (anti-D, anti-K, anti-Fy(a), anti-Jk(a), etc.)
Clinically significant antibodies are typically IgG, react at 37°C, and can activate complement or cause extravascular hemolysis. Examples include anti-D, anti-c, anti-E, anti-K, anti-Fy(a), anti-Jk(a), and anti-S. These antibodies require antigen-negative, crossmatch-compatible blood for transfusion. Cold-reactive IgM antibodies (anti-M, anti-N, anti-P1) are usually clinically insignificant.
What investigation must be performed when a transfusion reaction is suspected?
Answer: Stop transfusion, clerical check, visual inspection of post-transfusion sample for hemolysis, DAT, repeat ABO/Rh on pre- and post-transfusion samples
Transfusion reaction investigation includes: 1) Stop the transfusion immediately, 2) Clerical verification of patient and unit identification, 3) Visual inspection for hemolysis (pink/red serum), 4) DAT on post-transfusion sample, 5) Repeat ABO/Rh typing on pre- and post-transfusion samples, 6) Notify blood bank. Additional tests may include urinalysis, bilirubin, haptoglobin, and LDH.
What is the shelf life of refrigerated red blood cells stored in CPDA-1 anticoagulant?
Answer: 35 days
Red blood cells stored in CPDA-1 have a shelf life of 35 days at 1-6°C. With additive solutions (AS-1, AS-3, AS-5), the shelf life extends to 42 days. Proper storage temperature must be maintained and monitored continuously. Outdated units must be discarded to ensure adequate post-transfusion red cell recovery (>75% at 24 hours).
What is the difference between the direct antiglobulin test (DAT) and the indirect antiglobulin test (IAT)?
Answer: DAT detects antibodies already bound to patient red cells in vivo; IAT detects antibodies in patient serum that bind to test red cells in vitro
The DAT (direct Coombs test) detects IgG or complement already bound to the patient's red cells in the circulation (in vivo sensitization). The IAT (indirect Coombs test) detects free antibodies in patient serum that bind to test red cells during laboratory incubation (in vitro sensitization). The DAT is used for transfusion reaction investigation and autoimmune hemolytic anemia.
What is a type and screen versus a type and crossmatch?
Answer: Type and screen determines blood type and screens for antibodies; type and crossmatch additionally tests patient serum against a specific donor unit
A type and screen (group and screen) includes ABO/Rh typing and antibody screening. If a negative screen and no history of clinically significant antibodies exist, blood can be issued with an electronic (computer) crossmatch. A type and crossmatch includes the additional step of testing patient serum against a specific donor unit, required when clinically significant antibodies are present.