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Clinical Pathology > CP7-5 haemoglobinopathies & obstetric haematology > Flashcards

CP7-5 haemoglobinopathies & obstetric haematology Flashcards

1
Q

At what stage of pregnancy is haemoglobinopathy screening done?

A

At about 8 weeks

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2
Q

What is involved in haemoglobinopathy screening?

A

getting family history
FBC +/- HPLC
+/- partner testing

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3
Q

If a pregnancy is classed as high risk for haemoglobinopathy, what further investigations can be done?

A

Prenatal diagnostic testing +/- termination of affected prgenancies or pre-implantation diagnostic testing in IVF

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4
Q

When does postnatal haemoglobinopathy screening done?

A

At 5 days

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5
Q

How is newborn screening of haemoglobinopathy done?

A

With a heal prick test to analyse dried spot blood

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6
Q

What is the goal of postnatal haemoglobinopathy testing?

A

For early detection of haemoglobinopathy like sickle cell disease

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7
Q

What changes in pregnancy can lead to physiological anaemia and macrocytosis?

A

Mother’s plasma volume increases by 50%
Her red blood cell mass expands by 25%
Haemodilution occurs
Mean cell volume increases physiologically

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8
Q

At what stage of pregnancy will the mother have maximum haemodilution?

A

32 weeks

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9
Q

What level of haemoglobin is classed as anaemic in the 1st and 3rd trimester?

A

<110 g/L

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10
Q

What level of haemoglobin is classed as anaemic in the 2nd trimester?

A

<105 g/L

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11
Q

What leukocytes increase in pregnancy?

A

Neutrophils
Left shift in maturation of myelocytes/metamyelocytes

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12
Q

When in pregnancy is thrombocytopenia usually marked?

A

After 20 weeks

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13
Q

What is the platelet count in 6.6%-11.6% of women towards the end of pregnancy?

A

<150 x 10^9 per L

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14
Q

What is the usual platelet count in pregnancy?

A

> 70 x 10^9 per L

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15
Q

What are some pathological causes of thrombocytopenia in pregnant women that are NOT related to the pregnancy?

A

Production failure in the bone marrow
Viral infection like HIV or EBV
Sepsis
Type 2B vWD
Hypersplenism

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16
Q

What are some pathological causes of thrombocytopenia in pregnant women that ARE pregnancy associated?

A

Severe folate deficiency
Pre-eclampsia
HELLP syndrome
AFLP

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17
Q

What evidence is there that pregnancy is a pro-thrombotic state?

A

Evidence of platelet activation
Increase in procoagulant factors
Reduction in natural anticoagulants
Reduction in fibrinolysis
Increased markers of thrombin generation
Increased levels of coagulation factors

18
Q

At what point do changes in coagulation due to pregnancy revert to normal?

A

6-8 weeks post partum

19
Q

What are the characteristics of normal erythrocytes?

A

Bi-concave discs
No nucleus
Transports O2 and CO2
Production is controlled by erythropoietin released by the kidneys in response to tissue O2 conc

20
Q

What is haemoglobin?

A

A tetramer of globin chains (2x alpha and 2x non-alpha)which are each non-covalently bonded to a Haem

21
Q

What are the three types of haemoglobin?

A

Hb-A
Hb-F
Hb-A2

22
Q

What globin chains make up Hb-A?

A

2x alpha
2x beta

23
Q

What globin chains make up Hb-F?

A

2x alpha
2x gamma

24
Q

What globin chains make up Hb-A2?

A

2x alpha
2x delta

25
Q

What is the advantage of haemoglobin being a tetramer of globins?

A

Globins protect the haem from oxidation
Makes the molecules soluble
Allows for variation in oxygen affinity

26
Q

What haemoglobin is found in a foetus?

A

Hb-F

27
Q

What haemoglobin is found in adults? In what perctenages?

A

Hb-A = >95%
Hb-A2 = <3.5%
Hb-F = <1%

28
Q

What chromosome codes for the alpha globins for haemoglobin?

A

Chromosome 16

29
Q

What chromosome codes for the gamma , delta and beta globins in haemoglobin?

A

Chromosome 11

30
Q

At what week of development does haemoglobin production move to the liver and spleen?

A

10-12 weeks

31
Q

In later inter uterine life, where is haemoglobin produced by the foetus?

A

In the bone marrow and liver

32
Q

What haemoglobin is produced by the bone marrow?

A

Hb-A

33
Q

What are some Hb structural variants that can be produced in people with haemoglobinopathy?

A

Hb S - aka sickle cell
Hb C
Hb D
Hb E

34
Q

What usually causes structural variations of Hb?

A

A single base substitution in a globin gene leading to altered structure/function

35
Q

What causes thalassaemia (alpha and beta)?

A
  1. Changes in globin gene expression lead to reduced rate of normal globin chain synthesis.
  2. This causes an inbalance of alpha and beta chain production resulting in free globins chains
  3. Free globin chains damage red cell membranes
36
Q

What inheritance pattern is seen in haemoglobinopathy?

A

Autosomal recessive

37
Q

What is the theory as to why haemoglobinopathy disorders developed? How does this reflect on the worldwide distribution of haemoglobin disorders?

A

Having the variation gave a survival advantage against malaria thus there is a high distribution of haemoglobin disorders across the tropics where malaria is more prevalent

38
Q

What key tests are used in diagnosing haemoglobinopathies?

A

From testing FBC
Blood films
Hb electrophoresis
Isoelectric focusing
High performance liquid chromatography (HPLC)

39
Q

What are further/extra investigations/ specialist tests that can be done into haemoglobinopathies?

A

Heat stability tests with isopropanol
Looking at O2 dissociation curves
DNA analysis
Mass spectrometry
Kleihaur testing
Supravital staining
Sickle solubility

40
Q

What will investigations into a patient with heterozygous sickle cell trait look like?

A

Normal blood count - no anaemia
Hb electrophoresis will show presence of Hb-S (~45%) and Hb-A (~55%)

41
Q

How does heterozygous sickle cell trait affect a patient?

A

Will have no problems except if become extremely hypoxic or dehydrated

Clinical Pathology (65 decks)

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