Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Semester 4: Haematology > the blood transfusion laboratory > Flashcards

the blood transfusion laboratory Flashcards

1
Q

antigens

A

part of the surface of cells, all blood cells have antigens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

antibodies

A
  • protein molecules: immunoglobulins (Ig)
  • usually IgM or IgG
  • found in the plasma
  • these are produced by the immune system in response to a foreign antigen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the 2 clinically most important blood groups?

A

ABO & Rh

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the 3 factors that can stimulate antibody production?

A
  1. Blood transfusion (blood carrying antigens foreign to the patient)
  2. Pregnancy (Fetal antigens entering the maternal circulation)
  3. Environmental factors (naturally acquired e.g. anti-A)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

describe antigen reactions in the body

A

destruction of the cell:

  • directly when the cell breaks up in the blood stream (intravascular)
  • indirectly when liver and spleen remove antibody coated cells (extravascular)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

antigen reactions in the laboratory

A

reactions are normally seen as agglutination tests

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is agglutination?

A

is the clumping together of red cells into visible agglutinates by antigen-antibody reactions
* it results from the cross linking of antibodies and antigens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what can agglutination identify?

A

agglutination is antigen-antibody specific and so can identify the presence of the red cell antigen (blood grouping) and the presence of the antibody in the plasma (antibody screening)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

ABO incompatibility

A

A or B cells being transfused into someone with the anti-A or anti-B antibody: can activate complement causing intravascular haemolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what happens in intravascular haemolysis

A

RBCs lyse in the circulation releasing haemoglobin into the plasma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Phenotype A

A

antigen: A
antibodies: anti-B
frequency: 43%
genotype: AA/AO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Phenotype B

A

antigen: B
antibodies: anti-A
frequency: 9%
genotype: BB/BO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Phenotype 0

A

antigen: none
antibodies: anti-A and anti-B
frequency: 45%
genotype: OO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Phenotype AB

A

antigen: A and B
antibodies: none
frequency: 3%
genotype: AB

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Testing patient’s red cells with anti-A, anti-B and anti-D

A
  • agglutination shows that a particular antigen is on the red cells
  • no agglutination shows the antigen is absent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Testing patient’s plasma with A cells and B cells

A
  • agglutination shows that a particular antibody is in the plasma or serum
  • no agglutination shows the antibody is absent
17
Q

Rh grouping system

A

Most important antigen is called D.
People with D antigen are D positive (85% of UK)
People who do not produce any D antigen are D negative (15%)
The other 4 main antigens are known as C, c, E and e

18
Q

Rh typing

A
  • must be tested in duplicate

- the patient/ donor will be classified as D positive or negative

19
Q

what is the clinical significance of Rh?

A
  • Transfusion
    D antigen is very immunogenic and anti-D is easily stimulated - PREVENTION!
    All Rh antibodies are capable of causing severe transfusion reaction- ANTIBODY DETECTION
  • Pregnancy
    Rh antibodies are usually IgG and can cause haemolytic disease of the newborn.
    Anti-D is still most common cause of severe HDN
20
Q

how does haemolytic disease of the newborn arise?

A
  • Rh+ father
  • Rh- mother carrying her first Rh+ fetus. The Rh antigens can enter the mothers circulation during delivery
  • Due to exposure to the fetal Rh antibodies, the mother will develop anti-Rh antibodies
  • If the woman becomes pregnant with another Rh+ fetus, the anti-Rh antibodies cross the placenta and damage the RBCs
21
Q

laboratory testing for HDN?

A
  • blood group and antibody screen to identify risk of HDN

- may need prophylaxis

22
Q

RAADP

A

An injection of anti-D will bind to and remove any fetal D positive red cells in the circulation

23
Q

what is haemolytic transfusion reaction

A

serious complication that can occur after a bloodtransfusion. Thereactionoccurs when the red blood cells that were given during thetransfusionare destroyed by the person’s immune system.

24
Q

how does antibody screening occur?

A

Patients serum is mixed with 3 selected screening cells, incubated for 15 minutes at 37oc and then centrifuged for 5 minutes.

Any clinically significant antibodies reacting at body temp should be detected and then identified using panel of known phenotyped red cells.

Specific antigen negative blood can then be provided for these patients to avoid stimulating an immune response.

25
Q

what is zeta potential?

A

the positively charged ion cloud that surrounds RBCs

- IgGs are too small to overcome zeta potential

26
Q

what does low ionic strength saline do?

A

it is negatively charged so neutralises the zeta potential

IgG is now able to span the gap between RBCs

27
Q

Indirect Antibody Test

A

Used to detect IgG antibodies
LISS counteracts Zeta potential.
Results in agglutination

28
Q

Immediate spin cross match

A

Antibody screen is negative
Checking donor red cells against patients plasma
ABO check
Incubate for 2 – 5 minutes (room temp), spin and read.

29
Q

Full Indirect Antiglobulin test (IAT) cross-match

A

Antibody screen positive or patient has known antibody history.
Select antigen negative donor red cells and incubate with patient serum for 15 minutes at 37oC

30
Q

Red cell transfusion

A

Concentrated red cells (packed cells) in a suspension of SAGM

Red cells oxygen carrying capacity

Symptomatic anaemia

Exchange transfusion

If significant bleeding anticipated, activate the major haemorrhage protocol

31
Q

Fresh frozen plasma

A

FFP contains all clotting factors

Given for coagulopathy with associated bleeding

Requires clotting screens to monitor

Only has 24 hour life after thawing
(five days for major haemorrhage)

32
Q

Platelets

A

Adult pool of platelets from 4 donors (suspended in plasma from 1 donor)

Platelets required to create clots to reduce bleeding

Some drugs given to reduce efficacy of platelets (anti-platelet agents) so patient history important

33
Q

Cryoprecipitate

A

Contains Factor VIII, VWF and fibrinogen

2 units usually given at one time

Monitor fibrinogen levels by clotting screens

Semester 4: Haematology (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions