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Y2 Transfusion Science > Antenatal Testing > Flashcards

Antenatal Testing Flashcards

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1
Q

What does HDFN stand for?

A

Haemolytic Disease of the foetus and Newborn

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2
Q

What is the medical name for HDFN?

A

Erythroblastosis fetalis

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3
Q

When does HDFN occur?

A

When the mother has IgG red cell all-antibodies in her plasma that cross the placental barrier and bind to foetal red cells, processing the corresponding antigen.

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4
Q

In which birth is HDFN usually an issue and why?

A

The second birth.

The first child isn’t unaffected because the foetal and maternal circulation and separate. However, during the second pregnancy the foetal blood can be affected.

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5
Q

How is HDFN often recognised after birth?

A

Babies often have jaundice or high unconjugated bilirubin levels.

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6
Q

How does a Rh- negative mother become sensitised to Rh antigens?

A

By transfusion or previous birth of an Rh+ foetus.

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7
Q

What are the symptoms of HDFN?

A

Swollen liver.
Severe abdominal swelling.
Jaundice.
Kernicterus.

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8
Q

What are the signs of jaundice?

A

Yellowing of the skin and eyes.

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9
Q

What is Kernicterus?

A

Bilirubin accumulates in the grey matter of neurological tissue where is exerts direct neurotoxic effects.

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10
Q

How does Kernicterus cause neurotoxicity?

A

It causes mass destruction of neurones by apoptosis and necrosis.

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11
Q

What are the symptoms of Acute bilirubin encephalopathy in newborns?

A 
Lethargy
Decreased feeding 
Hypotonia
Hypertonia
High-pitched crying
Fever
Seizures
Death in some severe cases
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12
Q

What are some of the symptoms of Chronic Bilirubin encephalopathy in newborns?

A 
Movement disorders. 
Auditory dysfunction. 
Oculomotor impairments. 
Dental enamel hypoplasia. 
Gastroesophageal reflux. 
Impared digestive function.
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13
Q

What is dental enamel hypoplasia?

A

Degradation and decreased enamel on the teeth.

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14
Q

What is hypotonia?

A

Decreased muscle tone.

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15
Q

What is hypertonia?

A

Increased muscle tone.

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16
Q

What titre does Anti-Kell need to have to cause HDFN?

A

Any

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17
Q

How does Anti-Kell cause HDFN?

A

Anti-Kell surpasses the bone marrow by inhibiting erythroid progenitor cells. It can also cause alloimmune haemolytic anaemia.

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18
Q

Why is it important that women of child bearing age are transfused with Kell -ve blood?

A

To prevent HDFN caused by Anti-Kell

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19
Q

How quickly can HDFN caused by Anti-Kell be caused?

A

As early as 20 weeks

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20
Q

Why are routine antenatal tests carried out at 28 weeks?

A

To confirm ABO group and RhD group.

Detection and identification of red cell all-antibodies to exclude late development of red cell all-antibodies.

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21
Q

Why do we try to identify allo-antibodies before 28 weeks in the pregnancy?

A

Antibodies detected before 28 weeks are less likely to cause problems with the foetus.

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22
Q

What is ffDNA?

A

Free foetal DNA

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23
Q

What is ffDNA used for?

A

The foetal genotype can now be determined by PCR on trace amounts of free foetal DNA in the mother’s circulation.

It tests for RhD, D, c, R, e and Kell. If any of these factors are over the ideal limits, the mother will be referred to a foetal medical specialise.

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24
Q

How are levels of Anti D and Anti C measured in a sample?

A

Using a continuous flow analyser.
Amount of agglutination the antibody causes in compared to a British standard.
This is a quantification method.

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25
Q

How are levels of Anti-K, Anti-E and Anti-Fya measured in sample?

A

Test serial dilutions of the plasma with red cells carrying the corresponding antigens by IAT. The titre is the greatest dilution at which a reaction is found - the higher the titre, the more antibody present.

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26
Q

How does Anti-D prevent HDFN?

A

Anti-D immunoglobulin is given to the mother. This coats any RhD antigens on any RhD positive foetal cells in the maternal circulation. The RhD positive cells are removed by the spleen before the immune system can recognise them and cause and illicit response.

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27
Q

What does RAADP mean?

A

Routine Antenatal Anti-D Prophylaxis

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28
Q

What women are offered RAADP?

A

Women who are RhD negative but are having an RhD positive baby.

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29
Q

If a woman wants RAAP, when is this given in the pregnancy?

A

In a large dose at 28 weeks.

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30
Q

What effect does RAADP have when given?

A

It achieves a significant reduction in the incidence of maternal sensitisation to RhD from sensitisation events.

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31
Q

What is Prophylaxis?

A

Treatment given to prevent disease.

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32
Q

When should an assessment of FMH size occur?

A

Following a sensitisation event during pregnancy.

After 20 weeks gestation for RhD negative women.

Following delivery of a RhD positive baby if the woman is RhD negative.

Following a still birth for RhD positive or negative woman.

33
Q

Give some examples of sensitising events in pregnancy?

A 
Antepartum Haemorrhage. 
External Cephalic Version. 
Abdominal Trauma. 
Intrauterine death and still birth. 
In-utero therapeutics interventions. 
Miscarriage. 
Therapeutic termination of pregnancy.
34
Q

What is External Cephalic Version

A

External cephalic version (ECV) is a process by which a breech baby can sometimes be turned from buttocks or foot first to head first. It is a manual procedure that is recommended by national guidelines for breech presentation of a pregnancy with a single baby, in order to enable vaginal delivery.

35
Q

How does HbF differ to HbA?

A

It is more resistant to both acid and alkalis

36
Q

What is HbF?

A

Foetal haemoglobin

37
Q

What are the benefits of using the acid elution method to identify the volume of an FMH?

A

Quick and easy to perform.

38
Q

How does the cytometry method for measuring the volume of an FMH work ?

A

It is based on the detection of a minor population of RhD +ve cells with a fluorochrome conjugated IgG monoclonal anti-D reagent.

39
Q

Why can’t RhD +ve women use the flow cytometry method to measure their FMH volume?

A

anti-D flurorchrome is used.

40
Q

What are the disadvantages of using flow cytometry to decipher the volume of an FMH?

A

Expensive and required a lot of training to do.

41
Q

When may HFN be suspected?

A

Jaundice in new-born infants with no obvious cause.

Those babies born to mothers with known all-antibodies.

42
Q

What tests may be performed in the lab to investigate suspected HDFN?

A
  • ABO and RhD group on maternal and baby samples.
  • Antibody screen, panel and identification maternal sample.
  • DAT on baby sample.
43
Q

What blood type do mothers have when they are most likely to have HDFN due to ABO incompatibility?

A

O

44
Q

How frequently are high risk pregnancies monitored, why and using what methods?

A

Weekly by foetal doppler ultrasound scans to measure middle cerebral artery ear systolic velocity. This indicates the severity of foetal anaemia and regular ultrasound to monitor foetal growth.

45
Q

What indicates that foetal blood sampling may be needed ?

A
  • Severe anaemia before 24 weeks is suspected.
  • If the mother has had a previous intrauterine death.
  • If there is a rapid increase in maternal red cell alloantibody levels.
46
Q

What is intrauterine transfusion used for?

A

To prevent or treat life-threatening foetal anaemia and allow pregnancy to continue to a stage where a viable baby can be delivered.

47
Q

How are the hazards of Intrauterine transfusion reduced?

A

The transfusion is started is started as late as possible and the frequency of transfusion is reduced by giving the maximum safe volume of a special red cell component with a high haematocrit.

48
Q

What are top up and exchange transfusions used for in terms of pregnancy?

A

To treat new-borns who are still poorly due to being affected by maternal antibodies.

To treat severe hyperbilirubinemia and anaemia secondary to HDFN.

49
Q

What is the aim of top and exchange transfusions in new-borns?

A

To remove antibody coated red cells and excess bilirubin and increase haemoglobin.

50
Q

What are the risks of exchange transfusions in newborns?

A

Risk of morbidity and mortality due to vascular accidents, cardiac complications, biochemical and haematological disturbance and blood borne infections.

51
Q

What are the indications that newborns required exchange transfusions?

A

Severe hyperbilirubinemia caused by HDFN.

Rate of rise in serum bilirubin is too high.

Clinical signs of acute bilirubin encephalopathy.

52
Q

What are the clinical signs of acute bilirubin encephalopathy in children?

A 
Hypotonic
Lethargy
Hypertonia
Opisthothonos
Irritability
High pitched cry
53
Q

When are top up transfusions used for newborns?

A

For infants who have had a lot of blood removed for testing.

54
Q

Are top up transfusions used to treat HDFN?

A

No

55
Q

What are the requirements of the blood for neonatal top up transfusion?

A

O RhD negative
CDE -ve
CMV -ve
Not first time donor

56
Q

What class of antibody is associated with HDFN?

A

IgG

57
Q

Anti-Kell HDFN is associated with foetal anaemia rather than hyperbillirubinaemia, true or false?

A

True

58
Q

Which antibodies are quantified in HDFN?

A

Anti-c

Anti-D

59
Q

With ABO HDFN, what blood group is mum usually?

A

O

60
Q

A doppler ultrasound is used to measure foetal anaemia, true or false?

A

True

61
Q

Exchange transfusion is used to treat foetal anaemia in utero, true or false?

A

False

62
Q

What are foetal cell estimations used for?

A

Assessing the dose of anti-D immunoglobulin required for post-delivery Rh D negative mothers OR for estimating the severity of foetal bleeding in utero.

63
Q

What type of haemoglobin do foetal cells contain?

A

HbF

64
Q

What type of haemoglobin is normal adult haemoglobin?

A

HbA

65
Q

What are the issues with using the acid elution method to calculate the amount of foetal cells that are present in a sample?

A

Non-elution can occur
Over-elution can occur
There is often a broad spread of results if the same sample is sent to different hospitals

66
Q

What are the clinical issues with issuing Anti-D indicated by acid elution methods?

A

Some hospitals could issue doses of Anti-D which would not be enough to cover the FMH volume and some would be too much.

67
Q

What are the benefits of flow cytometry over acid elution methods when determining volume of FMH?

A

Much smaller range produced so is more reliable and accurate.

68
Q

What does FMH stand for?

A

Fetomaternal haemorrhage

69
Q

In the case of non or over elution when determining data for FMH, what should you do?

A 
Repeat all tests on freshly prepared slides. 
Use newly prepared reagents. 
Carefully check all timings. 
Clean Colin jars. 
Use thin films. 
Use a coverslip with immersion oil.
70
Q

During acid elution to find volume of FMH, why are the samples placed in Shepherds alcohol for 5 minds?

A

This adheres the cells to the slide.

71
Q

During acid elution to find volume of FMH, why are the samples eluted for 20 seconds?

A

This removes HbA from adult red cells

72
Q

During acid elution to find volume of FMH, why are the samples counter stained with erythrosine for 3 mins?

A

This stains any foetal cells which contain HbF.

73
Q

During acid elution to find volume of FMH, why are the samples diluted by 1 in 3?

A

This ensures a mono-layer of cells.

74
Q

In the red cell antibody practical, why are the samples centrifuged for 9 minutes?

A

Any agglutination will be trapped by the gel beads in the cassette column.

75
Q

Overall, what is the Keilhauer test used for and when may flow cytometry be used post this?

A

Keilhauer test is used to detect the FMH. Then if there is a positive result, flow cytometry is used to determine the FMH so that we know how much Anti-D to give.

76
Q

If ffDNA shows the baby is RhD -ve, do we need to give Anti-D?

A

No

77
Q

Why is there a 37 minute incubation time in the Keilhauer test?

A

This is the longest time that the human serum should take to react.

78
Q

What are the 3 events that may give someone antibodies?

A

Pregnancy, transfusion or transplant.

Y2 Transfusion Science (10 decks)

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