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Book - Transfusion Medicine for Pathologists > Ch. 4 - Blood bank testing > Flashcards

Ch. 4 - Blood bank testing Flashcards

1
Q

What are the 7 required steps for pretransfusion testing as dictated by the AABB?

A
  1. Patient identification and collection of sample
  2. Blood bank evaluation of sample
  3. Serology testing to include ABO+D
  4. Serology testing for other antibodies (screen)
  5. Selection of blood components
  6. Crossmatching of blood components
  7. Labeling and issuing of blood components
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2
Q

What information is required on any patient specimen label?

A
  1. Patient identification with at least two unique identifiers (usually name and MRN)
  2. Date of collection
  3. Phlebotomist collecting the sample
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3
Q

What are two examples of wrong blood in tube (WBIT) errors?

A
  1. Blood is taken from a wrong patient but is subsequently labeled with the info of the intended patient.
  2. Blood is collected from the intended patient but labeled with another patient’s information.
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4
Q

What is the risk of a wrong blood in tube (WBIT) error? How can they be reduced?

A

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.

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5
Q

What blood bank records are reviewed for a patient upon arrival of a pre-testing specimen?

A
  1. Previous ABO/Rh type (to catch WBITs)
  2. Any difficulties in typing the patient
  3. Any significant antibodies
  4. Any transfusion reactions
  5. Any special transfusion requirements
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6
Q

Describe the storage requirements of pretransfusion testing specimens.

A

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.

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7
Q

When does a type & screen expire?

A

Generally, 3 days later at midnight (with day of receipt counting as day 0).

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8
Q

Distinguish between pretransfusion testing requirements for RBC-containing units and eg. Plasma/platelets/cryo.

A

A 3-day valid type and screen is required for any RBC containing unit. All other blood components only require a historical type.

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9
Q

What are the important features of the isohemagglutinin antibodies?

A

They are naturally occuring, IgM-based, and can fix complement resulting in intravascular hemolysis.

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10
Q

Distinguish between forward and reverse typing.

A

Forward typing: Patient RBCs mixed with known antisera.

Reverse typing: Patient plasma mixed with phenotyped red cells (A1 and B)

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11
Q

What are the color of Anti-A and Anti-B antisera?

A

Anti-A - Blue

Anti-B - Yellow

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12
Q

ABO discrepancies: What are some causes for increased forward typing reactivity?

A

Acquired antigens (acquired B, B(A) phenomenon)
ABO mismatch from stem cell transplant
Nonspecific agglutination
Out of group transfusion with mixed-field effect

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13
Q

ABO discrepancies: What are some causes for increased reverse typing reactivity?

A

Cold reactive auto/alloantibodies
Passive transfer of antibodies (eg IVIG, plasma mismatch)
A2 subgroup patient with A1 antibodies
Increased serum protein

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14
Q

ABO discrepancies: What are some causes for decreased forward typing reactivity?

A

Decreased antigen due to hematologic malignancy
Massive transfusion
Weak ABO subgroup
Newborns with weak ABO subgroup

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15
Q

ABO discrepancies: What are some causes for decreased reverse typing reactivity?

A

Immunosuppression / transplant pateints
Elderly or newborn patients
Hypogammaglobulinemia

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16
Q

Who should have weak D testing?

A

All newborn and donor units. Testing for weak D is not required by a transfusion service.

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17
Q

How is ABO/Rh typing different for neonates?

A

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.

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18
Q

Should whole blood be matched as in an RBC-containing unit or as in a plasma containing unit

A

Both; it should be type-matched to the patient. (actually, plasma/minor mismatch is okay)

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19
Q

In what situations is electronic crossmatching acceptable?

A

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.

20
Q

What are the six components of the final check before a blood product is released?

A
  1. Patient identifiers, ABO/Rh type
  2. Donation identifiers, ABO/Rh type
  3. Interpretation of crossmatch results
  4. Any special transfusion requirements
  5. Expiration date and time of product
  6. Date and time of issuing
21
Q

Distinguish between the structure of most clinically significant and insignificant antibodies.

A

Significant: Usually IgG, warm-reacting and requiring immune stimulus.
Nonsignificant: IgM pentamers reacting at colder temperatures (exception: Isohemagglutinins)

22
Q

Which antigens are required by FDA to be tested for on serologic evaluation?

A 
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)
23
Q

What are the physical components of the indirect antiglobulin test?

A

Patient plasma/serum, reagent RBCs, and anti-human globulin (AHG).

24
Q

What potentiating agents can be used during incubation to help antigen-antibody interactions overcome zeta potential?

A

LISS
PEG
22% bovine albumin

25
Q

What are the three different testing systems used in pretransfusion evaluation?

A

Tube-based system (add AHG)
Gel-based system (AHG is impregnated in matrix)
Solid-state system (indicator RBCs are already AHG-bound)

26
Q

What is the “rule of 3” in antibody idenfication?

A

One should demonstrate at least 3 cells positive for an antigen that agglutinate and at least 3 cells negative that do not.

27
Q

What antigens tend to show dosage effect on antibody workup? What is the consequence of this?

A

Rh, Kidd, Duffy, MNS. These antibodies must be ruled out on a homozygous screening cell.

28
Q

What is the purpose of antibody neutralization?

A

Can be used to confirm an antibody or allow for more clear investigation of other potential antibodies.

29
Q

What are the some sources of neutralizing substances for ABO antibodies? For Lewis?

A

ABO: An individual secretor with relevant isohemagglutinin
Lewis: An individual secretor that has the Lewis gene

30
Q

What are some sources of neutralizing substances for P1 antibodies? Sd(a) antibodies? Chido/Rodgers antibodies?

A

P1: Pigeon egg white, hydatid cyst fluid
Sd(a): Human urine
Chido/Rodgers: Human serum

31
Q

What antigens are destroyed by enzyme treatment?

A

MNS, Duffy, Lutheran

32
Q

What antigens are enhanced by enzyme treatment?

A

Rh, Kidd, carbohydrate antigens generally (ABO, I, P, Lewis)

33
Q

How is Kell affected by enzyme treatment? Sulfhydryl reduction?

A

Enzyme treatment has no effect. Treatment with eg DTT or 2-ME remove the Kell antigens.

34
Q

What are some sources of lectins for the A1 antigen? H antigen?

A

A1: Dolichos biflorus
H: Ulex europaeus

35
Q

What is the autocontrol?

A

Patient’s RBC is added to patient’s plasma/serum; this is run when the antibody screen is positive and may catch coating by alloantibodies, autoantibodies, or antibodies to enhancement media

36
Q

What are the three types of DAT reagents?

A

Anti-IgG
Anti-C3d
Polyspecific (both)

37
Q

What is the significance of a positive autocontrol but negative DAT? What about if the DAT is positive?

A

Negative DAT: Probably antibody to enhancement media.

Positive DAT: May represent recently transfused cells, autoantibodies, or drugs/autoimmune dz

38
Q

What is the purpose of elution?

A

Allows for uncoupling of antibodies from coated RBCs. Can be ran against a panel of donor cells to determine specificity of the antibodies.

39
Q

What is the purpose of adsorption studies?

A

Allows for removal of autoantibodies from coated RBCs to aid identification of underlying alloantibodies.

40
Q

When should phenotyping not be attempted?

A

Following transfusion of RBCs (will see mixed field and/or phenotype the donor cells)

41
Q

How does red cell genotyping work?

A

RBC antigen profile is determined from DNA testing obtained from leukocytes.

42
Q

Identify the reaction pattern: Selective cells that are reactive with the same strength. (AC negative)

A

A single alloantibody

43
Q

Identify the reaction pattern: Selective cells that are reactive with varying strength. (AC negative)

A

Multiple alloantibodies or a single alloantibody showing dosage.

44
Q

Identify the reaction pattern: Panreactivity with negative autocontrol.

A

Alloantibodies to high frequency antigens or antibodies to preservatives.

45
Q

Identify the reaction pattern: Panreactivity with positive autocontrol.

A

Autoantibodies vs antibody to enhancement media (perform DAT to distinguish).

Book - Transfusion Medicine for Pathologists (13 decks)

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