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Transfusion Science > Lecture 6 - Neonatal Testing > Flashcards

Lecture 6 - Neonatal Testing Flashcards

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1
Q

what is HDFN?

A

haemolytic disease of the foetus and newborn

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2
Q

how does HDFN occur?

A

when the mother has IgG antibodies in her blood that cross the plasma and bind to foetal red cells that possess the corresponding antigen

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3
Q

what is hydrops fetalis?

A

heart failure in utero

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4
Q

how can HDFN cause heart failure in utero?

A

the anaemia causes cardiac decompensation due to lack of red cells

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5
Q

what is extramedullary erythropoiesis?

A

red cells being produced in an unusual location

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6
Q

how can HDFN cause jaundice?

A

the removal of the erythrocyte antibody complex from foetal blood circulation causes haemaglobin degradation so causes increased unconjugated bilirubin levels

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7
Q

how does bilirubin levels cause neurological damage? what is this called?

A

called kernicterus and it is caused by bilirubin accumulating in the grey matter of neurological tissue causing neurotoxic effects

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8
Q

how is the neurotoxicity caused in kernicterus?

A

mass destruction of neurones via apoptosis and necrosis

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9
Q

what are the symptoms of acute bilirubin encephalopathy?

A

legarthy, decreased feeding, hypotonia/hypertonia, high-pitched cry, fever, seizures or death

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10
Q

what are the features of chronic bilirubin encephalopathy?

A

movement disorders, auditory dysfunction, oculomotor impairments, impaired digestive function, gastroesophageal reflex

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11
Q

what is different in relation to HDFN with an IgG antibody and an anti-Kell antibody?

A

anti-kell can cause severe anaemia regardless of the strength of the antibody

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12
Q

what are the effects of an anti-Kell antibody on red blood cells?

A

it suppresses the bone marrow so inhibits erythroid pregenitor cells, prevents formation of blood cells

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13
Q

what are the microbiology antenatal tests?

A

HPB, HIV, syphilis

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14
Q

what are the transfusion antenatal tests?

A

ABO group, antibody screening, ffDNA

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15
Q

when do microbiology and transfusion tests occur?

A

8-12 weeks gestation

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16
Q

what is the purpose of 28 week tests?

A

to confirm ABO and RhD group, for detection and identification of alloantibodies

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17
Q

how is the genotype of the baby determined?

A

using PCR on free foetal DNA in the mothers circulation

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18
Q

what is the ffDNA genotyping sensitive for?

A

RhD, C, c, E, e and Kell

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19
Q

what concentration of anti-D levels cause referral to a foetal medicine specialist?

A

above 4IU/mL

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20
Q

what concentration of anti-c causes referral to foetal medicine specialist?

A

above 7.5IU/mL

21
Q

what type of antibodies are quantified?

A

anti-D and anti-c

22
Q

how does quantification work?

A

amount of agglutination the antibody causes compared to the standard that runs at the same time

23
Q

what machine does quantification occur in?

A

continuous flow analyser

24
Q

what antibodies are used in titration?

A

anti-K, anti-E, anti-Fya

25
Q

how does the titration reaction occur?

A

serial dilutions of patient plasma are made and red cells added, the titre is the same as the highest dilution in which a reaction is found

26
Q

how does anti-D Ig injection work?

A

the injection coats the RhD antigens on any D+ foetal cells in the maternal circulation to mask them from the immune system to then be removed by the spleen

27
Q

what is RAADP?

A

routine antenatal anti-D prophylaxis

28
Q

how much RAADP is administered and when?

A

15000 IU at 28 weeks gestation

29
Q

what patients are given RAADP?

A

those who are RhD negative that have RhD positive baby

30
Q

what causes foeto-maternal haemorrhage?

A

foetal blood crosses maternal circulation

31
Q

how much FMH can the dosage of RAADP given protect against?

A

12mL for 1500IU

32
Q

when should as assessment of FMH occur?

A

following a sensitising event on a RhD negative woman, following delivery of RhD positive baby, following stillbirth/IUD on negative or positive women

33
Q

what is the acid equation method?

A

dry blood films are tied and immersed in an acid buffer, HbA is denatured and leaves behind blood ghosts, yet HbF are resistant and can be stained, therefore determines if HbF is present

34
Q

how does flow cytometry occur?

A

a fluorochrome conjugated IgG anti-D antibody reagent is used, passed through a laser so that the population of both types of haemoglobin can be identified and populations determined

35
Q

why cant flow cytometry be used on a RhD positive woman?

A

because an anti-D fluorochrome antibody is used

36
Q

when is suspected HDFN investigated?

A

when unexpected jaundice occurs, babies born to mothers with known alloantibodies

37
Q

how is HDFN investigated?

A

test for maternal antibodies, test for ABO incompatibility

38
Q

how is HDFN investigation performed?

A

ABO and RhD grouping performed on mother and baby samples, antibody screening panel and NAT on baby sample

39
Q

what blood group does a mother usually belong to when HDFN occurs?

A

usually a group O with a group A/B baby

40
Q

what is the doppler ultrasound?

A

determines the middle cerebral artery peak systolic velocity, which indicates the severity of the foetal anaemia

41
Q

what things indicate the need for foetal blood sampling?

A

severe anaemia before 24 weeks gestation, if there has been a post IUD, if there is an increase in maternal red cell alloantibody levels

42
Q

what is the purpose of IU transfusions?

A

prevent life threatening foetal anaemia and allow pregnancy to continue until the baby is viable

43
Q

how are IU transfusions adapted to lower the risk?

A

started as late as possible, and maximum safe volume with maximum haemocrit is given to lessen frequency

44
Q

what is exchange transfusions used to treat?

A

severe hyperbilirubinaemia and anaemia secondary to HDFN

45
Q

what is the aim of exchange transfusions?

A

to remove antibody coated red cells and excess bilirubin and increase haemoglobin

46
Q

what causes such a high risk from IUT’s?

A

cardiac complications, biochemical and haematological disturbances

47
Q

what is the indications for a IUT?

A

severe hyperbilirubinaemia caused by HDFN, symptoms of ABH

48
Q

what conditions worsen HDFN?

A

septicaemia, metabolic disease and DIC

49
Q

what are the requirements of top up blood?

A

O-, CDE-, Kell-, CMV-, first time donors, same donor and preferably male

Transfusion Science (8 decks)

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