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3003 Transfusion science > Pre-transfusion testing > Flashcards

Pre-transfusion testing Flashcards

1
Q

What do you do if you receive a sample in a TM lab that doesn’t fulfil the labelling requirements?

A
  • must NOT be accepted -> recollect
  • request must have ≥3 unique Identifiers
  • identifiers on request form & tube must match
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2
Q

Summarise the ABO/Rh grouping requirements for pre-transfusion testing.

A
  • Must perform a Group & Screen (ABO group & Ab screen)
  • GROUP: do FWD & RVS group
  • Not require RVS group for infants <4months bc Aby from mum
  • confirm ABO/RhD match (do confirmatory test if new patient)
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3
Q

why don’t we need to use Aby that detects DVI in prenatal & postnatal maternal specimens

A

bc little evidence DVI+ (Ag) sensitises mum

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4
Q

In the case of an ABO discrepancy, which RBCs do you issue for transfusion if they are required before the discrepancy can be resolved? *& case of preg. woman

A 
O Rh(D) neg blood units
* O neg & K neg cells for preg. woman = avoid HDNB
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5
Q

Explain why O cells are used for aby screening.

A
  • not have A, B, A,B Ag

- Specific to detect Aby from RH or other blood groups

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6
Q

Explain why homozygous Jk, Fy, and Ss cells are required in aby screening and ID*

A
  • consider zygosity of Jk, Fy and Ss due to dosage
  • bc heterozygous expression = weak reaction (bc slightly less [ ] of that Ag)
  • vs homozygous = strong expression
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7
Q

What testing is the TM lab required to perform on donor cells?

A
  • Crossmatch by IS or IAT
  • > IS: if patient has NO history of clin. sig Aby
  • > IAT: if patient has history of clin. sig Aby
  • blood chosen should be Ag neg to patient’s Aby
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8
Q

Females of childbearing potential should receive what blood units?

A

Match ABO & RhD and K

*If in emergency = O neg & K neg

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9
Q

If pateint has Aby NOT considered as clinically sig. (e.g._), [test] @ _ºC should be selected for transfusion & Ag [do/don’t] need to be Ag Neg

A

a) anti -A1, -P1, -Lea, -Leb, -Lea+b, -HI, autoanti-I (other cold agglutinants)
b) IAT @ 37ºC
c) don’t need to be Ag Neg

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10
Q

What RBC units should you select & what test if patient history has no (or doubtful) CLin sig Aby and NOT currently reactive by IAT @37ºC

A
  • ABO compatible RBC w/out doing IAT

- OR select Ag neg cells

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11
Q

What is phenotyping, and when is it performed during pre-transfusion testing?

A
  • Phenotyping: determine the expression (of RBC) - blood group
  • used for paternal phenotypingto determine is the father is Rh(D) Pos or Neg (when mum is Rh(D) neg) bc determine if baby is Rh(D) pos or neg
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12
Q

Discuss the selection of plasma products for transfusion recipients.

A
  • Same ABO group as patient
  • Group AB universal plasma product
  • Rh(D) neg recipients can receive RhD pos plasma
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13
Q

Order of group preference when choosing a plasma product for recipient that is O group. & plt product

A 
plma : plts
O :1st: O
A :2nd: A (*express A2)
B :3rd: B 
4th: AB
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14
Q

Order of group preference when choosing a plasma product for recipient that is A group. & plt product

A

plma : plts
A :1st: A
AB :2nd: B or O(*lo titre Ab or Pooled)
B (low titre = low Aby) :3rd: AB

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15
Q

Order of group preference when choosing a plasma product for recipient that is B group. & plt product

A

plma : plts
B :1st: B
AB :2nd: A or O (*lo titre Ab or Pooled, A2)
A (low titre = low Aby) :3rd: AB

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16
Q

Order of group preference when choosing a plasma product for recipient that is AB group. & plt product

A

AB :1st: AB
A (low titre = low Aby) :2nd: A or B (lo titre Ab or Pooled)
B (low titre = low Aby) :3rd: O (lo titre Ab or Pooled)

17
Q

Order of group preference when choosing a plasma product for recipient that is unknown group. & plt product

A

AB :1st: A or O (*lo titre Ab or Pooled, A2)

A (low titre = low Aby) :2nd:

18
Q

Discuss the selection of platelet products for transfusion recipients.

A
  • preferably match ABO/Rh as patient
  • but Match ABO desirable > RhD
  • If Rh(D) neg recipients receive RhD pos plts MUST be given RhD-Ig = minimise I.Sys making RhD Ab
19
Q

In an emergency, are you required to complete pre-transfusion testing before issuing blood product?
Explain your answer.

A
  • RBC: Transfuse O Neg blood (E- & K-) to give (while grouping current sample)
  • plasma: give group AB (or Ab @ low titre)
  • Plt: ABO may not need to match (but may need to give Ab?)
20
Q

what instances should you reject a sample and ask for a re-collect?

A
  • request not have ≥3 unique Identifiers
  • identifiers on request form & tube don’t match
  • haemolysed sample
21
Q

Explain the scenarios where samples for TS testing are valid for 72 hours, and 7 days (and up to 3 months*)

A
  1. If patient not transfused or pregnant in past 3 months = sample is valid for 7 days from collection
  2. If patient has been transfused or preg. in past 3 months = sample is valid for 72 hours (3 days) from collection [bc inc. risk for amnestic response]
    * patient not preg or transfused in at 3 months, and is having surgery
22
Q

What is the shelf life of RBCs? Platelets? Why is the platelet shelf life shorter?

A

a) RBC stored @ 2-6ºC for max. 42 days
b) Plt stored @ 20-24ºC for 5 days (w/ gentle agitation)
c) bc stored @ room temp. = inc. risk of bacterial contamination

23
Q

why do we use an anti-A,B Ab as well in FWD grouping for baby’s grouping?

A

bc better at detecting subgroups

24
Q

reasons for a positive XM in 1) IS and 2) IAT

A

1) Neg Aby screen but incompatible XM
- recipient & donor are ABO incompatible
- recipient produce cold Aby (react @ RT)
- ABO subgroup
2) Neg Aby screen but incompatible IAT XM
- Donor has pos. DAT
- recipient has Aby to low incidence Ag

25
Q

In an emergency situation, if a patient has a negative Aby screen, what is an acceptable time frame for the provision of packed red cells?
b) what is Aby screen was pos?*

A

(10 min to ABO/Rh grouping)

a) 30 min: Ab screen & XM
b) >30min (~45-60 min)??

26
Q

What is a “computer crossmatch”, and in which circumstances may it be used?

A
  • electronic XM
  • when donor RBC released w/out physically doing XM
    • used when patient has NO CLIN. SIG ABYS OR HISTORY
    • lab has validated data management system
    • Perform pre-transfusion testing on CURRENT patient sample
27
Q

Distinguish between a “major” crossmatch and a “minor” crossmatch. Why are minor crossmatches not required?*

A

Major: Donor cells XM against recipient’s plasma
Minor: Recipient’s cells are XM against donor plasma
* minor XM not required bc the main goal is to avoid HTR to recipient [test their plasma] (not donor)

3003 Transfusion science (7 decks)

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