Haematology

Question 1

When is anti-D administered?

Answer 1

Weeks 28 + 34 + < 72 hours following birth

+ if there is a sensitising event

Question 2

Why can ABO incompatibility occur with a first pregnancy?

Answer 2

Maternal anti-A/B antibodies are present from birth

These are usually IgM antibodies but may also be IgG antibodies which can cross the placenta​

Question 3

What % of newborns with ABO compatibility are symptomatic?

Answer 3

5-10%

Maternal antibodies are usually IgM and cannot cross the placenta

Question 4

How does the Coombs test help distinguish ABO and Rhesus incompatibility?

Answer 4

+ve in Rhesus

• ve or weakly +ve in ABO
• A and B antigens are less well developed in neonates than in older children and adults*
• Antigenic sites are fewer and farther apart on neonatal RBCs*

Question 5

How does a peripheral blood smear differentiate ABO and Rhesus incompatibility?

Answer 5

Spherocytosis in ABO incompatibility due to partial membrane loss

Question 6

How is haemolytic disease of the newborn and foetus treated prenatally?

Answer 6

Intrauterine blood transfusion

Question 7

What are the harms of iron deficiency in an infant

Answer 7

Long-term effects on neurodevelopment and behaviour

Question 8

What is involved in a haemolytic screen?

Answer 8

Reticulocyte count

Direct antiglobulin test (whether red cells have been coated in antibodies and/or complement)

Lactate dehydrogenase

Bilirubin

Question 9

What is the most common bleeding disorder of childhood?

Answer 9

Idiopathic thrombocytopenic purpura

Question 10

When is the peak age for ITP?

Answer 10

4-8 years

Question 11

What is the pathophysiology of ITP?

Answer 11

Antiplatelet antibodies attach to platelets → platelets are destroyed by splenic macrophages

Question 12

What is the prognosis of ITP in infants?

Answer 12

Benign, 80% recover by 6 months

Platelets usually return to normal in 1-3 weeks

Question 13

Why can excess milk cause iron deficiency?

Answer 13

Calcium inhibits iron absorption

Question 14

How is hyperbilirubinaemia in infants with haemolytic disease of the infant and newborn treated?

Answer 14

Phototherapy

UV oxidises and breaks down bilirubin

Question 15

What is the triad of HUS?

Answer 15

1. Low platelets (petechiae)
2. Microangiopathic haemolytic anaemia (jaundice, fatigue, pallor)
3. Impaired renal function (oliguria)

Question 16

What are the most common causative agents in HUS?

Answer 16

Enterohaemorrhagic E. coli (shiga-like toxin)

Shiga toxin (Shigella dysenteriae)

Streptococcus pneumoniae infection

Question 17

Atypical lymphocytosis is characteristic of which disease?

Answer 17

Infectious mononucleosis

Question 18

What are the most common causes of haemolytic uremic syndrome?

Answer 18

Bacterial exotoxins (Shiga toxin; Shiga-like toxin (enterohaemorrhagic E. coli, usually from food poisoning)

Streptococcus pneumoniae

Question 19

Which age group does HUS predominantly affect?

Answer 19

Children < 5

Question 20

What laboratory test best differentiates HSP from HUS?

Answer 20

HSP - elevated platelets

HUS - low platelets

Question 21

What classically preceedes HSP?

Answer 21

Infection

Most commonly an URTI caused by group A Streptococcus

Question 22

What is the pathophysiology of HSP?

Answer 22

Antigen → IgA production → IgA immune complexes → complement activation → vascular inflammation and damage

Question 23

What murmur is associated with a PDA?

Answer 23

Loud continuous murmur

Best heard in the left infraclavicular region

Question 24

Hypersegmented polymorphonuclear cells are characteristic of which condition?

Answer 24

Megaloblastic anaemia

Question 25

What clotting factor is deficient in haemophilia A?

Answer 25

VIII

Question 26

Which clotting factor is deficient in haemophilia B?

Answer 26

IX