HDN

Question 1

Describe the pathophysiology of HDN

Answer 1

• HDN / HDNB / HDFNB (F= foetus)
• jaundice: elevated (>300 uM) &/or rapid inc. (>8.5 uM/hr) serum bilirubin w/in 24hr or 14+ days post partum
• Positive DAT: maternal Ab bound on Bb’s RBC
• severe HDN -> kernicterus, hydrops fetalis

Question 2

Which antibodies commonly cause HDN?

Answer 2

IgG Aby reactive @ IAT

• Anti-c, -K, ABO
• Rhesus, Kell, Duffy, MNS, Kidd, ABO

Question 3

Summarise the serological testing required during the ante and post natal periods.

Answer 3

• Ante-: @ first trimester visit: ABO & Rh(D) typing & Ab screen
• Retest in 28 weeks for ABO & Rh(D) type and Ab screen if neg.
• Post-:
  • Mum have ABO & Rh(D) and Ab screen (if not done already)
  • Bb: if mum is Rh(D) neg or has CSig. Ab = do ABO/Rh(D) group, DAT, Hb, Bilirubin, elution studies on baby
• IF DAT positive => Ab screen

Question 4

What are the requirements for blood products used in intrauterine transfusions?

Answer 4

• <5 days old
• ABO/Rh compatible w/ mum & foetus OR O neg cells
• *K neg
• Ag neg to maternal Ab (not want to give blood that’ll lyse bc from mum’s Aby)
• CMV neg
• Irradiated
• HCT ≥70% (bc not want vol. overload)
• XM compatible w/ maternal or infant plasma

Question 5

2 test for determining foetal anaemia is baby @ risk of HDN (e.g. bc baby K+)

Answer 5

• Quantification/titration
• Middle cerebral artrey (MCA) Doppler ultrasound:
  • non-invasive
  • Velocity of blood flow in MCA
  • inc blood flow = anaemia

Question 6

In which scenarios are CMV-negative blood products required for transfusion?

Answer 6

• CMV-seroneg
• at-risk patients:
  • Transplant recipients
  • immunosuppressive chemo
  • intrauterine transfusion
  • neonate
  • preg. women

Question 7

In which scenarios are irradiated blood products required for transfusion?

Answer 7

• HLA-matched transfusions
• Intrauterine transfusion
• Newborns
• Immunodeficiency

Question 8

What are CMV-negative blood componenets

Answer 8

• negative to cytomegalovirus - carried from WBC

Question 9

What is irradiated blood components & it’s purpose

Answer 9

• RBC, plts treated w/ 25-50 Gy y-radiation
• prevent transfusion-assoc graft-vs-host disease
  • prevent proliferation of donor T-lymphocytes

Question 10

Describe why it is important to differentiate anti-D+C and anti-G in the management of HDN.

Answer 10

• bc someone producing anit-G (OR anti-G +C) can receive Rh(D)Gg
• BUT someone producing anti-D + C is not bc already produce/have immune anti-D
• differentiate using G- or D- differnetiation

Question 11

Describe how serological testing of the father is beneficial in management of HDN

Answer 11

• perform XM w/ maternal plasma & paternal RBC
• bc father may produce low incidence Ag => baby inherits => will sensitize mum
• consider when there’s HDN w/ pos DAT but neg Aby screen for mum & ABO compatibility b/w mum & baby

Question 12

Treatment options for HDNB

Answer 12

• phototherapy

- Exchange transfusion: intrauterine

Question 13

how can you determine if a person has acquired or immune anti-D?

Answer 13

• probs prophylactic if anti-D quant is low

- immune: if quant. is stable or rising

Question 14

Differentiate Rh(c) HDN w/ Rh(D) HDN

Answer 14

• Rh(c): present similar to HDN to Rh(D) incompatibility

- note: there’s is no prophalactic anti-c

Question 15

Describe the G Ag

Answer 15

• An Ag on Rh blood group

- Present on C & D Ag = C+ and/or D+

Question 16

How can you distinguish if a person has Anti-G or instead has 2 Aby, anti-C + D?

Answer 16

• Anti-C + D: Anti-D stronger than Anti-C

* Anti-G: reaction to anti-C (D-C+ cells) stronger than anti-D (D+C- cells)

Question 17

interpret Rh(c) quant with risk of HDN

Answer 17

<7.5: unlikely risk to HDN
7.5-20: moderate risk to HDN
>20: High risk to HDN

Question 18

How does anti-K differ to anti-D HDN (features of Kell HDN)

Answer 18

• previous history not indicate severity
• poor correlation b/w Aby titre & disease severity
• haemolysis not a dominant feature ≠ elevated bilirubin
  = anaemia from insuffiecient erythropoeisis due to dec production as anti-K binds to K Ag on erythroid progenitor cells

Question 19

ABO HDN

Answer 19

• high titre of IgG in mum (can go through placenta)
• elevated bilirubin w/o significant anaemia in foetal RBC: bc baby;s ABO Ag not fully developed
• sensitised cells not lysed = DAT pos (not always)
• spherocytes

Question 20

Describe the tests for foetomaternal haemorrhage

Answer 20

• Acid elution / Kleihauer / - Betke test: Expose blood film to acid = denatures HbA (adult) => stain intact HbF (foetus) w/ erythrosine / eosine
• Flow cytometry: detect D pos cells in maternal blood using Fluorescent-labelled anti-D Ab

Question 21

what needs to be done if mum has anti-K Aby

Answer 21

• refer to specialist
• phenotype/genotype father
• > if father is K+ genotype baby’s DNA from maternal plasma
• > if baby is K+, do MCA doppler& perform intrauterine transfusion if necessary