Ch. 4 - Blood bank testing Flashcards
What are the 7 required steps for pretransfusion testing as dictated by the AABB?
- Patient identification and collection of sample
- Blood bank evaluation of sample
- Serology testing to include ABO+D
- Serology testing for other antibodies (screen)
- Selection of blood components
- Crossmatching of blood components
- Labeling and issuing of blood components
What information is required on any patient specimen label?
- Patient identification with at least two unique identifiers (usually name and MRN)
- Date of collection
- Phlebotomist collecting the sample
What are two examples of wrong blood in tube (WBIT) errors?
- Blood is taken from a wrong patient but is subsequently labeled with the info of the intended patient.
- Blood is collected from the intended patient but labeled with another patient’s information.
What is the risk of a wrong blood in tube (WBIT) error? How can they be reduced?
About 1 in 2000 specimens. This can be reduced by examination of historical blood type (to catch discrepancies) and requiring a second sample if there is no historical type.
What blood bank records are reviewed for a patient upon arrival of a pre-testing specimen?
- Previous ABO/Rh type (to catch WBITs)
- Any difficulties in typing the patient
- Any significant antibodies
- Any transfusion reactions
- Any special transfusion requirements
Describe the storage requirements of pretransfusion testing specimens.
Kept refrigerated for at least 7 days to allow for later reaction workups. Also kept with a segment of any RBC-containing unit sent for that patient.
When does a type & screen expire?
Generally, 3 days later at midnight (with day of receipt counting as day 0).
Distinguish between pretransfusion testing requirements for RBC-containing units and eg. Plasma/platelets/cryo.
A 3-day valid type and screen is required for any RBC containing unit. All other blood components only require a historical type.
What are the important features of the isohemagglutinin antibodies?
They are naturally occuring, IgM-based, and can fix complement resulting in intravascular hemolysis.
Distinguish between forward and reverse typing.
Forward typing: Patient RBCs mixed with known antisera.
Reverse typing: Patient plasma mixed with phenotyped red cells (A1 and B)
What are the color of Anti-A and Anti-B antisera?
Anti-A - Blue
Anti-B - Yellow
ABO discrepancies: What are some causes for increased forward typing reactivity?
Acquired antigens (acquired B, B(A) phenomenon)
ABO mismatch from stem cell transplant
Nonspecific agglutination
Out of group transfusion with mixed-field effect
ABO discrepancies: What are some causes for increased reverse typing reactivity?
Cold reactive auto/alloantibodies
Passive transfer of antibodies (eg IVIG, plasma mismatch)
A2 subgroup patient with A1 antibodies
Increased serum protein
ABO discrepancies: What are some causes for decreased forward typing reactivity?
Decreased antigen due to hematologic malignancy
Massive transfusion
Weak ABO subgroup
Newborns with weak ABO subgroup
ABO discrepancies: What are some causes for decreased reverse typing reactivity?
Immunosuppression / transplant pateints
Elderly or newborn patients
Hypogammaglobulinemia
Who should have weak D testing?
All newborn and donor units. Testing for weak D is not required by a transfusion service.
How is ABO/Rh typing different for neonates?
Since isohemagglutinins only develop around 5 months of age, reverse typing is only performed if a nongroup-O neonate will receive nongroup-O RBCs that are not compatible with mom’s ABO type.
Should whole blood be matched as in an RBC-containing unit or as in a plasma containing unit
Both; it should be type-matched to the patient. (actually, plasma/minor mismatch is okay)
In what situations is electronic crossmatching acceptable?
When the antibody screen is negative and there is a valid historical or current type on file with no history of allo- or auto-antibodies.
What are the six components of the final check before a blood product is released?
- Patient identifiers, ABO/Rh type
- Donation identifiers, ABO/Rh type
- Interpretation of crossmatch results
- Any special transfusion requirements
- Expiration date and time of product
- Date and time of issuing
Distinguish between the structure of most clinically significant and insignificant antibodies.
Significant: Usually IgG, warm-reacting and requiring immune stimulus.
Nonsignificant: IgM pentamers reacting at colder temperatures (exception: Isohemagglutinins)
Which antigens are required by FDA to be tested for on serologic evaluation?
Rh (D, C, E, c, e) Kell (K, k) Duffy (Fya, Fyb) Kidd (Jka, Jkb) Lewis (Lea, Leb) P (P1) MNS (M, N, S, s, U)
What are the physical components of the indirect antiglobulin test?
Patient plasma/serum, reagent RBCs, and anti-human globulin (AHG).
What potentiating agents can be used during incubation to help antigen-antibody interactions overcome zeta potential?
LISS
PEG
22% bovine albumin
