HCS329 revision exercises with answers PDF

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Summary

Revision exercises These are to help your revision – the questions are quite focussed and detailed, but you should look at the questions, and think about why they are true or false, and read the notes relating to the topic. Focus on: Theory behind the question eg. relating to the pathogenesis of a d...

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HCS329 Haematology & Transfusion Science Revision exercises These are to help your revision – the questions are quite focussed and detailed, but you should look at the questions, and think about why they are true or false, and read the notes relating to the topic. Focus on: •

Theory behind the question eg. relating to the pathogenesis of a disease

•

Test results ie general findings of a FBC (you do not need to know reference ranges) or blood film, plus other additional diagnostic tests for a particular disease

•

Basis of any techniques (used in screening and/or diagnosis) if relevant

Remember the exam questions are essay questions and your answers should demonstrate depth of knowledge and understanding of the topic, which is directly relevant to the question, alongside correct data interpretation (if required) and clarity of the argument/structure of the answer.

Haemolytic anaemia and haemoglobinopathies

1. Which of these statements are NOT TRUE concerning the red cell? A) The mature red blood cell is a ‘flexible sack’ of haemoglobin B) When stained with a rowmanowsky dye, Azure B binds to Hb, giving the cell its red appearance under the microscope C) It generates energy as adenosine triphosphate (ATP) by the anaerobic glycolytic (Embden-Meyerhof) pathway D) It generates reducing power as NADH by glycolysis and as reduced nicotinamide adenine dinucleotide phosphate (NADPH) by the hexose monophosphate shunt (pentose phosphate pathway) E) It generates 2,3-diphosphoglycerate by the pentose phosphate pathway A) True B) False - When stained with a rowmanowsky dye, eosin binds to Hb, giving the cell its red appearance under the microscope C) True D) True – NADH can reduce Fe3+ to Fe2+ via MetHb reductase, and NADPH can generate glutathione which prevents cellular damage by free radicals E) False – 2,3-DPG is produced by the Rapoport-Leubering shunt

2. Which of these are TRUE concerning the red cell membrane? A) B) C) D) E)

Phospholipids are symmetrically disposed across the red cell membrane Spectrin and ankyrin are extracellular proteins that reinforce the membrane Band 3 is an essential component of the red cell membrane where it functions as an anion transporter Excess surface area to volume ratio of the red cell is essential for deformation Inherited defects in membrane proteins can cause hereditary spherocytosis

HCS329 Haematology & Transfusion Science A) False - Cholesterol is distributed evenly and is an essential structural component of cell membranes that is required to establish proper membrane permeability and fluidity. The phospholipids are asymmetrically disposed, with charged phosphatidlyethanolamine and phosphatidylserine (PS) on the inner layer, and uncharged phosphatidyl choline and sphingomyelin on the outer layer. B) False - They are intracellular, and are components of the two complexes which maintain vertical links between the membrane and cytoskeleton C) True – Band3 also has a structural function – it links the lipid bilayer to the underlaying membrane skeleton D) True E) True

3. Which of these are TRUE about red cell aging? A) B) C) D)

A high concentration of molecular oxygen and iron (in Hb) carry a danger of ROS formation Autoxidation of Hb (Fe2+) to metHb (Fe3+) produces superoxide (O2.-) Superoxide dismutase is part of the red cell antioxidant defence Glutathione peroxidase together with reduced glutathione (GSH) is able to scavenge and reduce hydrogen peroxide and prevent damage by reactive oxygen species E) Band 3 plays a key role in physiological red cell aging F) All of the above

A) True – red cells also take up ROS released from other cells such as neutrophils, macrophages and endothelial cells B) True – superoxide dismutase then catalyses the dismutation of superoxide to H2O2, and enzymes such as catalase and glutathione peroxidase scavenge peroxides C) True D) True – Reduced glutathione (GSH) is formed by the action of glutathione reductase and NADPH, where NADPH is produced from the reaction catalysed by glucose 6 phosphate dehydrogenase in the pentose phosphate pathway. GSH is essential for the reduction of hydrogen peroxide and oxygen radicals and the maintenance of haemoglobin, sulfhydryl-containing enzymes and membrane thiols (compounds containing –SH group(s)), allowing erythrocytes to carry large quantities of oxygen safely. E) True – partially deoxygenated Hb binds to band 3, localising ROS production to the membrane, leading to band 3 oxidation, antigen exposure and autologous IgG binding (and removal of cells via extravascular haemolysis), Also, hemichrome (further oxidised and denatured metHb) binding to band 3 disrupts vertical membrane-cytoskeleton linkages and triggers band 3 clustering, further increasing IgG binding.

4. Which of the following causes of anaemia would NOT normally be characterized by a microcytosis? A) B) C) D)

Thalassaemia Iron deficiency Acute blood loss Chronic blood loss

C) Acute blood loss results typically in normocytic anaemia, as predominantly dilutional; chronic blood loss, by contrast, will result in iron deficiency and thus microcytosis. In iron deficiency and thalassaemia there is a

HCS329 Haematology & Transfusion Science problem with haemoglobin production, resulting in small red blood cells because extra cell divisions occur before a critical haemoglobin concentration is reached to arrest mitosis.

5. A 20-year-old man has seen his GP due to unusual tiredness. Initial blood tests reveal the following results (normal range): Hb 9g/dl (12-15) and MCV 97fl (77-98). The blood film and biochemical tests indicate red cell destruction mainly by extravascular haemolysis. Which are the most likely diagnoses? A) B) C) D) E)

Iron deficiency anaemia Thalassaemia G6PD deficiency anaemia Hereditary spherocytosis Sickle cell disease

A) Expect a microcytic anaemia without haemolysis B) Cells are removed by extravascular haemolysis, but the anaemia would be microcytic C) Cells can be removed by both intravascular and extravascular haemolysis (evidence of intravascular haemolysis would likely be observed) D) Correct – a normocytic anaemia, with red cells removed by extravascular haemolysis E) Correct - Membrane abnormalities from sickling and oxidative damage caused by hemoglobin S, along with impaired deformability of sickle cells, leads to splenic trapping and removal of cells by extravascular haemolysis (2/3rd red cells destroyed this way). 1/3rd cells undergo intravascular haemolysis. 6. An asymptomatic 20-year-old woman from South-East Asia presents for the first time with the following blood count: Hb 11g/dl (12-15), MCH 25pg (26-33) and MCV 64fl (77-98). Her ferritin is at the top end of the normal range. Which is the most likely diagnosis? A) B) C) D)

Iron deficiency anaemia Sickle cell trait Beta thalassaemia major alpha zero thalassaemia trait (loss of 2 alpha genes)

A) B) C) D)

The high-normal ferritin makes this less likely. Not typically associated with a microcytosis. Thalassaemia major is transfusion dependent, incompatible with this patient’s history. Correct – carrier status, expect to see low Hb, low MCV and MCH

7. A couple who both carry the sickle trait have recently had a child with sickle cell disease. Which of the following statements regarding their child are INCORRECT? A) B) C) D)

His disease is likely to be problematic in the first year of life Prophylactic penicillin treatment is advised Young children can develop potentially life-threatening acute splenic sequestration HbS is insoluble and polymerises, forming long fibres which result in sickle shaped red cells under deoxygenated conditions E) Sickle cell disease is a qualitative haemoglobinopathy F) The full blood count will show low haemoglobin, elevated MCHC, and lowered reticulocyte count

HCS329 Haematology & Transfusion Science A) This is incorrect - Fetal Hb (containing gamma rather than beta globin chains) is still expressed in infancy and so the disease is unlikely to be problematic in the first year of life. B) Consistent with UK guidelines for asplenic patients, sickle patients are also recommended to take regular penicillin. C) This is a crisis caused by the rapid and extensive trapping of red cells in the spleen, leading to profound anaemia, massive splenomegaly, and increased risk of a fatal infection D) Correct E) Correct - as opposed to thalassemia which is a quantitative haemoglobinopathy F) False - the FBC will show low haemoglobin, elevated MCHC, and elevated reticulocyte count

8. A patient with a mild microcytic anaemia has Hb electrophoresis testing. She is found to have bands corresponding to HbA, HbA2, HbS and HbF. Which of the following is the MOST LIKELY diagnosis? A) B) C) D)

Sickle cell anaemia Sickle cell trait Beta thalassaemia Alpha thalassaemia

A) The presence of normal beta globin chains in HbA excludes this option. B) Correct - Both sickle and normal beta globin chains must be synthesized to assemble globins detected here C) The presence of HbS excludes this as the sole diagnosis. D) The presence of HbS excludes this as the sole diagnosis.

9. Anaemias may be accompanied by a reticulocytosis in cases where the bone marrow is able to make a compensatory increase in erythroid output. In which of the following anaemias would an appropriate reticulocytosis be expected? A) B) C) D) E)

Folate deficiency Hereditary spherocytosis Autoimmune haemolytic anaemia Beta-thalassaemia Untreated iron deficiency

A) A low reticulocyte count would be expected. B) Correct - Erythroid expansion is seen in the marrow to compensate for the increased peripheral destruction of red cells. C) Correct – as for B D) Correct – excess alpha chains precipitate in the red blood cells, leading to premature destruction and bone marrow compensation E) Without iron treatment, the marrow is unable to mount a sufficient response to anaemia.

10. An 18-year-old woman presents with splenomegaly and the following blood count: Hb 7g/dl (1215), MCH 22pg (26-33) and MCV 60fl (77-98). The blood film shows microcytic, hypochromic red cells, and Heinz bodies are visible in a supravital stain. Which of the following statements are TRUE concerning this patient?

HCS329 Haematology & Transfusion Science A) B) C) D) E)

She has beta thalassaemia Heinz bodies are comprised of precipitated haemoglobin H Transfusion support may be required later in life HbH can only be detected by HPLC analysis HbA2 microcolumn chromatography is diagnostic for alpha thalassaemia

A) False – she has alpha thalassaemia (HbH disease) B) True - Normal adult hemoglobin is composed of two alpha and two beta chains. Alpha thalassemia patients have partial or complete defects in alpha globin production, leading to a relative abundance of beta globin chains in the cell. These excess beta globin chains aggregate to form HbH, which has decreased solubility and precipitates in the red blood cell cytoplasm. C) True D) False – HbH can be detected by other haemoglobin separation techniques (electrophoresis and capillary electrophoresis) E) False – this test is diagnostic for beta-thalassaemia (HbA2 = α2δ2)

11. A previously well 35-year-old man visits his general practitioner with fatigue, breathlessness and palpitations. His GP notes pallor and requests a full blood count, which returns the following results: Hb 7g/dl, MCV 99fl (77-99), WBC 8x10^9/l (4-10), Platelets 360 x 10^9/l (150-400). A blood film shows spherocytes and polychromasia, but no red cell fragmentation and no other abnormalities of note. Which of the following is TRUE? A) B) C) D) E)

This is likely to represent intravascular haemolysis An indirect antiglobulin test is the next best investigation An elevated unconjugated bilirubin level would be expected His reticulocyte count would be expected to be low His serum haptoglobin will be undetectable

A) False - Typically, red cell fragments (schistocytes) would be seen on the blood film in intravascular haemolysis. B) False - Spherocytes can also be seen in patients with autoimmune haemolytic anaemia, a direct antiglobulin test would be a suitable investigation to assess whether red cells are coated with antibody. A negative DAT will strongly suggest HS. C) True - The breakdown products of haemoglobin will accumulate as unconjugated bilirubin. D) False - Increased red cell destruction would be expected to result in a compensatory reticulocytosis. E) False - Haptoglobin binds free haemoglobin and is then cleared from the circulation. Extremely low/undetectable levels are more charateristic of intravascular haemolysis.

12. A diagnosis of hereditary spherocytosis is being considered in an 18-year-old woman with a longstanding reticulocytosis and mild splenomegaly. Which of the following would BEST support a diagnosis of HS? A) B) C) D)

family history of anaemia A positive EMA test A positive direct antiglobulin test Presence of spherocytes on the blood film

A) No - Although this may be positive, many cases of HS occur without a family history.

HCS329 Haematology & Transfusion Science B) Yes - Demonstrates a loss of key membrane components. EMA (eosin-5-maleimide) is a fluorescent dye which binds mainly to band 3. In HS, the amount of bound dye is reduced compared to control RBCs C) No - Would not be expected to be positive in HS. D) No - While these would be expected, they are not diagnostic, being present in autoimmune haemolysis as well, for example.

13. A 5-year-old Cypriot boy is brought to his GP with jaundice following antibiotic treatment for an upper respiratory tract infection. A blood film shows anaemia, polychromasia and occasional ‘bite cells’. Further questioning reveals that his brother has been treated for intermittent anaemia. Which is the most likely diagnosis? A) B) C) D) E)

Pyruvate kinase deficiency Hereditary spherocytosis G6PD deficiency Alpha thalassaemia Beta thalassaemia trait

C) G6PD deficiency - A common condition in the Mediterranean, typical history of episodic anaemia following an oxidant challenge (e.g. some antibiotics).

14. Which statement is FALSE regarding haemolytic anaemia? A) There are over 140 known mutations in the G6PD gene, most of which are point mutations B) Class II G6PD variants produce enzyme with less than 10% activity, but patients do not have chronic anaemia C) G6PD assays should not be performed on samples collected after a haemolytic episode as G6PD levels may be falsely elevated due to reticulocytosis D) Unstable Hbs can precipitate in red blood cells, damage the membrane, causing splenic entrapment and phagocytosis by macrophages E) Defects in red cell membrane proteins (eg band 3, spectrin) results in uncoupling of the connections between the lipid bilayer and cytoskeleton. This results in spherocyte formation, which are removed from the circulation by intravascular haemolysis A) True - Glucose 6 phosphate dehydrogenase catalyses the conversion of glucose-6-phosphate to 6phosphoglucono-δ-lactone, the first and rate-limiting step in the pentose phosphate pathway. B) True – WHO classification is based on clinical symptoms and enzyme activity C) True - reticulocytes have increased G6PD activity compared to mature erythrocytes D) True - Instability caused by substitution of a charged for an uncharged amino acid (eg HbS), substitution of amino acids in a/b chains at the subunit binding (contact) points, or abnormal composition (eg b-tetramers in alpha-thalassaemia) E) Loss of connections cause RBCs to lose unsupported lipid membrane over time (vesicles), with little loss of volume. RBCs acquire a decreased surface area to volume ratio and become spherical. Cells have reduced deformability and survival in spleen is decreased. As spherocytes attempt to move through the narrow fenestrations of endothelial cells lining the splenic sinusoids, they acquire further membrane loss or become trapped and are rapidly removed by macrophages. Also, as red cells are sequestered, the membrane becomes more damaged, cells lose more membrane and become more spherical (as a result of this conditioning), possibly enhanced by acidic conditions (pH

HCS329 Haematology & Transfusion Science falls in red cell stasis) in the spleen and prolonged contact of cells with macrophages, and ROS released from macrophages.

Haematological malignancies

15. Flow cytometry is used for the diagnosis of many haematological conditions. In which of the following situations would it NOT be useful? A) B) C) D) E)

Defining B cell clonality, in a case of lymphocytosis Detecting small populations of abnormal cells following treatment Defining lineage specification in haematopoietic malignancies Analysis of tissue sections Anaemia A) This is a typical investigation in persistent lymphocytosis, and can help determine whether a population of cells is monoclonal or polyclonal and therefore whether there is a malignant or reactive population of cells. B) This is an expanding use of flow cytometry (e.g. following treatment for AML). C) Some cases of acute leukaemia are difficult to classify by morphological features only, and flow cytometry will define lineage-specific cell surface markers. D) Correct - This is not possible by flow cytometry, for which cells must be in suspension (e.g. blood or bone marrow aspirate). E) Correct – flow cytometry would not be useful do detect an anaemia

16. Which of the following statements is FALSE regarding acute leukaemia? A) B) C) D)

t(15;17) defines acute promyelocytic leukaemia AML is the most common acute form of leukaemia in adults The presence of Auer rods in leukaemic blasts signifies these are myeloblasts The presence of malignant cells in the bone marrow does not affect bone marrow function A)

True – this results in the PML-RARA fusion gene. The fusion gene is not responsive to retinoic acid (regulates genes needed for granulocyte maturation) and therefore the cells are arrested at the promyelocyte stage B) True C) True D) False – there must by >20% blasts in the BM to be classified as an acute leukaemia, and accumulation of blast cells in the BM can lead to bone marrow failure (anaemia with thrombocytopenia)

17. A 40-year-old man presents with fatigue, weight loss and splenomegaly. A full blood count shows: Hb 10g/dl (13.3-16.7), WBC 170x109/l (4-10), Platelets 420x109/l (150-400). His blood film is reported as showing a massive excess of mature and maturing myeloid cells with left shift to myelocytes, and some nucleated red cells. Which of the following statements are TRUE?

HCS329 Haematology & Transfusion Science A) Acute myeloid leukaemia is the most likely diagnosis B) Chronic myeloid leukaemia is the most likely diagnosis C) The clinical symptoms are due to anaemia, hypermetabolism, and the storage of excess blood cells in the spleen D) The BCR-ABL1 fusion gene is present in only 5% CML patients E) Serum uric acid is usually lowered A) False - The marked excess of mature cells is not consistent with AML, where a block to maturation and the accumulation of blasts would be expected. B) True – A typical picture for CML C) True - The clinical symptoms are fatigue (caused by anaemia), weight loss (hypermetabolism due to high numbers of white cells) and splenomegaly. This patient may also experience increased risk of infection (neutrophils not functioning properly) or easy bruising/bleeding (abnormal platelet function). (petechiae – small red/purple spots due to broken capillaries and minor haemorrhage; ecchymoses – hematoma of the skin, localised collection of blood outside vessels) D) False – the is the most common translocation and is present in 95% CML patients E) False – serum uric acid is usually raised and reflects increased cell turnover (purine breakdown) and can lead to renal failure and gout

18. Which of th...