Haematology Flashcards
Difference between whole blood, blood plasma and serum ?
Whole blood = everything i.e. includes RBCs, WBCs and platelets
Blood plasma = Fluid portion of the blood i.e. excludes RBCs, WBCs and platelets.
Serum = what’s left after the clotting factors are removed from blood plasma.
What does serum contain ?
- Glucose
- Electrolytes e.g. sodium, potassium
- Proteins such as immunoglobulins and hormones
Blood cells develop in the bone marrow. Bone marrow is mostly found in the pelvis, vertebrae, ribs and sternum. Pluripotent haematopoietic stem cells are undifferentiated cells that have the potential to transform into a variety of blood cells. They initially become what ?
- Myeloid stem cells (develop in the bone marrow)
- Lymphoid stem cells (develop in the lymphatic tissue)
- Dendritic cells (via various intermediate stages)
How are RBCs formed + what is their lifespan ?
They develop from reticulocytes (immature RBCs) that come from the myeloid stem cells. Their lifespan is approximately 120 days.
How are platelets formed + what is their lifespan
They are made by megakaryocytes that come from myeloid stem cells. Thier lifespan is 10 days.
Myeloid stem cells become myeloblasts that produce ?
- Monocytes then macrophages (in the tissues)
- Neutrophils
- Basophils
- Eosinophils
- Mast cells
Lymphocytes come from the lymphoid stem cells and become B cells or T cells. Where do B cells mature and what do they differentiate into + where do T cells mature and what do they differentiate into ?
B lymphocytes mature in the bone marrow and differentiate into:
- Plasma cells
- Memory cells
T lymphocytes in the thymus gland and differentiate into:
- CD4 cells (T helper cells)
- CD8 cells (cytotoxic T cells)
- Natural killer cells
What do each of these blood film findings mean and where can they be seen :
- Anisocytosis
- Target cells
- Heinz bodies
- Reticulocytes
- Schistocytes
- Sideroblasts
- Smudge cells
- Spherocytes
- Anisocytosis: Refers to a variation in the size of RBCs. These can be seen in myelodysplasic syndrome as well as some forms of anaemia.
- Target cells: have a central pigmented area, surrounded by a pale area, surrounded by a ring of thicker cytoplasm on the outside. This makes it look like a bull’s eye target. These can be seen in iron deficiency anaemia and post-splenectomy.
- Heinz bodies: Are individual blobs seen inside RBCs cause by denatured globin. They can be seen in G6PD and alpha-thalassaemia
- Reticulocytes: Are immature RBCs that are slightly larger than standard erythrocytes and still have RNA material in them. The RNA has a reticular (“mesh like”) appearance inside the cell. It is normal for about 1% of RBCs to be reticulocytes. This % goes up where there is rapid turnover of RBCs such as haemolytic anaemia. They demonstrate that the bone marrow is active in replacing lost cells.
- Schistocytes: Are fragments of RBCs. They indicate the RBCs are being physically damaged by trauma and during their journey through the blood vessels. They may indicate networks of clots in small blood vessels caused by HUS, DIC or thrombotic thrombocytopenic purpura. They can also be present in replacement metallic heart valves and haemolytic anemia.
- Sideroblasts: Are immature RBCs that contain blobs of iron. They occur when the bone marrow is unable to incorporate iron into the haemoglobin molecules. They can indicate myelodysplasic sydndrome.
- Smudge cells: Are ruptured WBCs that occur during the process of preparing the blood film due to aged or fragile WBCs. They can indicate chronic lymphocytic leukaemia.
- Spherocytes: Are spherical RBCs without the normal bi-concave disk shape. They can indicate autoimmune haemolytic anaemia or hereditary spherocytosis
What is anaemia ?
A low level of haemoglobin in the blood.
Note: This is the result of an underlying disease and is not a disease itself.
You can diagnose a pt with anaemia when they have a low haemoglobin. When you find an anaemic pt you should also check what ?
Mean cell volume (MCV)
Anaemia is subdivided into three main categories, what are they ?
Microcytic anaemia (low MCV) Normocytic anaemia (normal MCV) Macrocytic anaemia (high MCV)
Causes of microcytic anaemia ?
TAILS
T - Thalassaemia A - Anaemia of chronic disease I - Iron defiency anaemia L - Lead poisoning S - Sideroblastic anaemia
Causes of normocytic anaemia ?
3 As and 2 Hs
A - Acute blood loss A - Anaemia of chronic disease A - Aplastic anaemia H - Haemolytic anaemia H - Hypothyroidism
Macrocytic anaemia can but into two different categories, what are they ?
Megaloblastic or normoblastic
What is megaloblastic anaemia the result of ?
Impaired DNA synthesis preventing the cell from dividing normally. Rather than dividing it keeps growing into a large, abnormal cell.
Note: This is caused by a vitamin deficiency.
What is megaloblastic anaemia caused by ?
- B12 deficiency
- Folate deficiency
Normoblastic macrocytic anaemia is caused by ?
- Alcohol
- Reticulocytosis (usually from haemolytic anaemia or blood loss)
- Hypothyroidism
- Liver disease
- Drugs such as azathioprine
Name 6 generic symptoms of anaemia ?
- Tiredness
- SOB
- Headaches
- Dizziness
- Palpitations
- Worsening of other conditions such as angina, heart failure or peripheral vascular disease
Name 2 symptoms specific to iron deficiency anaemia ?
- Pica - describes dietary cravings for abnormal things such as dirt
- Hair loss
Name 4 generic signs of anaemia ?
- Pale skin
- Conjunctival pallor
- Tachycardia
- Raised resp rate
Name some signs of specific causes of anaemia ?
- Koilonychia - can indicate iron deficiency
- Angular chelitis - can indicate iron deficiency
- Atrophic glossitis - is a smooth tongue due to atrophy of the papillae and can indicate iron deficiency
- Brittle hair and nails can indicate iron deficiency
- Jaundice occurs in haemolytic anaemia
- Bone deformities occur in thalassaemia
- Oedema, HTN and excoriations on the skin can indciate CKD.
Investigations for anaemia (both initial and further) ?
Initial:
- Hb
- MCV
- B12
- Folate
- Ferritin
- Blood film
Further investigations:
- Oesophago-gastroduodenoscopy (OGD) and colonoscopy to investigate for a GI cause of unexplained iron deficiency anaemia. This is done on an urgent cancer referral for suspected GI cancer
- Bone marrow biopsy may be required if the cause is unclear.
Scenarios when iron stores can be used up and the pt can become iron deficient ?
- Insufficient dietary iron
- Iron requirements increase e.g. pregnancy
- Iron is being lost e.g. bleeding from a colon cancer
- Inadequate iron absorption
Where is iron mainly absorbed ?
In the duodenum and jejunum.
What does iron require to keep it in a soluble form + what form is this + what is the insoluble form/ when does this occur?
Acid from the stomach.
Fe2+ (ferrous) form.
When the acid level drops it changes to the insoluble Fe3+ (ferric) form.
Which medications can interfere with iron absorption ?
Medications that reduce stomach acid e.g. PPIs as they reduce the amount of stomach acid being produced
What conditions can cause inadequate iron absorption ?
Conditions that result in inflammation of the duodenum or jejunum e.g. coeliac disease or Crohn’s disease.
Causes of iron deficiency anaemia?
- Blood loss is the most common cause in adults
- Dietary insufficiency is the most common cause in growing children
- Poor iron absorption
- Increased requirements during pregnancy
Note:
The most common cause of iron deficiency anaemia in adults is blood loss. In menstruating women, particularly women with menorrhagia there is a clear source of blood loss. In women that are not menstruating or men the most common source of blood loss is the GI tract. It is important to be suspicious of a GI tract cancer. Oesophagitis and gastritis are the most common causes of GI tract bleeding. IBD should also be considered.
How does iron travel in the blood ?
As ferric ions (Fe3+) bound to transferrin.
What is the total iron binding capacity (TIBC) ?
It basically means the total space on the transferrin molecule for the iron to bind
How do you calculate transferrin saturation ?
Serum iron / total iron binding capacity
What is ferritin ?
The form that iron takes when it is deposited and stored in cells.
When is extra ferritin released from cells ?
In inflammation such as with infection or cancer
What does a low serum ferritin suggest ?
Highly suggestive of iron deficiency.
Note:
High ferritin is difficult to interpret and is likely to be related to inflammation rather than iron overload. A pt with a normal ferritin can still have iron deficiency anaemia, particularly if they have reasons to have a raised ferritin such as infection.
Serum iron varies significantly throughout the day with higher levels when ?
In the morning and after eating iron containing meals.
Note: On its own serum iron is not a very useful measure
Total iron binding capacity (TIBC) can be used as a marker for what ?
How much transferrin is in the blood.
Note: It is an easier test to perform than measuring transferrin
How do both TIBC and transferrin levels respond in iron deficiency and in iron overload ?
They both increase in iron deficiency and decrease in iron overload.
Note:
Transferrin saturation gives a good indication of the the total iron in the body. In normal adults it is around 30%.
What two things can increase the values of the previous tests mentioned giving the impression of iron overload ?
- Supplementation with iron
- Acute liver damage (lots of iron is stored in the liver)
Management of new iron deficiency in an adult without a clear underlying cause ?
New iron deficiency in an adult without a clear underlying cause e.g. menorrhagia or pregnancy should be investigated with suspicion. This involves doing an OGD and a colonoscopy to look for cancer of the gastrointestinal tract.
Management of iron deficiency anaemia (methods arranged from fastest to slowest and most invasive to least invasive) ?
- Blood transfusion: This will immediately correct the anaemia but not the underlying iron deficiency and also carries risks.
- Iron infusion e.g. “cosmofer”: There is a very small risk of anaphylaxis but it quickly corrects the iron deficiency. It should be avoided during sepsis as iron “feeds” bacteria.
- Oral iron e.g. ferrous sulphate 200 mg three times daily: This slowly corrects the iron deficiency. Oral iron causes constipation and black coloured stools. It is unsuitable where malabsorption is the cause of the anaemia.
Note: When correcting iron deficiency anaemia with iron you can expect the haemoglobin to rise by around 10 grams/litre per week.
Pernicious anaemia is a cause of which type of anaemia ?
B12 deficiency anaemia
B12 deficiency anaemia can be caused by which two things ?
Insufficient dietary intake of vitamin B12 or pernicious anaemia.
Pathophysiology of pernicious anaemia ?
The parietal cells of the stomach produce intrinsic factor which is essential for the absorption of vitamin B12 in the ileum. Pernicious anaemia is an autoimmune condition where antibodies form against the parietal cells or intrinsic factor. A lack of intrinsic factor prevents the absorption of vitamin B12 and the pt becomes vitamin B12 deficient.
Vitamin B12 deficiency can cause neurological symptoms. Name some of these ?
- Peripheral neuropathy with numbness or paraesthesia
- Loss of vibration sense or proprioception
- Visual changes
- Mood or cognitive changes
Tom tip:
For your exams remember testing vitamin B12 deficiency and pernicious anaemia in pts presenting with peripheral neuropathy, particularly with pins and needles
Diagnosis of pernicious anaemia ?
Testing for auto-antibodies is used to diagnose:
- Intrinsic factor antibody is the first line investigation
- Gastric parietal cell antibody can also be tested but is less helpful
Management of pernicious anaemia ?
Note: Dietary deficiency can be treated with oral replacement with cyanocobalamin unless the deficiency is severe.
Pts can be treated with 1 mg of IM hydroxycobalamin 3 times weekly for 2 weeks, then every 3 months. More intense regimes are used where there are neurological symptoms.
Note: If there is also folate deficiency it is important to treat the B12 deficiency first before correcting the folate deficiency. Treating pts with folic acid when they have a B12 deficiency can lead to subacute combined degeneration of the cord.
Haemolytic anaemia note:
There are a number of inherited conditons that cause RBCs to be more fragile and break down faster than normal, leading to chronic haemolytic anaemia. There are also a number of acquired conditions that lead to increased breakdown of RBCs and haemolytic anaemia
Inherited haemolytic anaemias ?
- Hereditary spherocytosis
- Hereditary elliptocytosis
- Thalassaemia
- Sickle cell anaemia
- G6PD deficiency
Acquired haemolytic anaemias ?
- Autoimmune haemolytic anaemia
- Alloimmune haemolytic anaemia (transfusion reactions and haemolytic disease of newborn)
- Paroxysmal nocturnal haemoglobinuria
- Microangiopathic haemolytic anaemia
- Prostatic valve related haemolysis
Features + explanation of haemolytic anaemia ?
The features are a result of the destruction of RBCs:
- Anaemia due to the reduction in circulating RBCs
- Splenomegaly as the spleen becomes filled with destroyed RBCs
- Jaundice as bilirubin is released during the destruction of RBCs
Investigations for haemolytic anaemia ?
- FBC shows a normocytic anaemia
- Blood film shows schistocytes (fragments of RBCs)
- Direct Coombs test is positive in autoimmune haemolytic anaemia.
What is hereditary spherocytosis + is it AD or AR ?
It is the most common inherited haemolytic anaemia in northern Europeans. It causes sphere shaped RBCs that are fragile and easily break down when passing through the spleen.
It is an autosomal dominant condition
How does hereditary spherocytosis present ?
It presents with jaundice, gallstones, splenomegaly and notably aplastic crisis in the presence of parvovirus.
Investigations for hereditary spherocytosis ?
It is diagnosed by FH and clinical features with spherocytes on the blood film. The MCHC is raised on a FBC. Reticulocytes will be raised due to rapid turnover of RBCs.
Management of hereditary spherocytosis ?
Treatment is with folate supplementation and splenectomy. Cholecystectomy may be required if gallstones are a problem.
Hereditary elliptocytosis ?
It is very similar to hereditary spherocytosis except that the RBCs are ellipse shaped. It is AD. Presentation and management are the same as hereditary spherocytosis.
What is G6PD deficiency ?
A condition where there is a defect in the RBC enzyme G6PD causing RBCs to break down early. Haemolytic crises can be triggered by infections, medications or fava beans (broad beans),
How does G6PD deficiency present + how is it diagnosed ?
It presents with jaundice (usually in the neonatal period), gallstones, anaemia, splenomegaly and Heinz bodies on blood film. Diagnosis can be made doing a G6PD enzyme assay.
Medications that trigger haemolysis in G6PD deficiency ?
Primaquine, ciprofloxacin, sulfonylureas, sulfasalazine and other sulphonamide drugs.
TOM TIP:
The key piece of knowledge for G6PD deficiency relates to triggers. In your exam look out for a pt that becomes jaundiced and becomes anaemic after eating broad beans, developing an infection or being treated with antimalarials. The underlying diagnosis might be G6PD deficiency.
What are the two types of autoimmune haemolytic anaemia (AIHA) ?
- Warm type autoimmune haemolytic anaemia
- Cold type autoimmune haemolytic anaemia
Warm type autoimmune haemolytic anaemia:
The more common type of AIHA. It occurs at normal or above normal temperatures. It is usually idiopathic.
Cold type autoimmune haemolytic anaemia:
Also called cold agglutinin disease. At lower temperatures the antibodies against RBCs attach themselves to RBCs and cause them to clump together. This is called agglutination. This results in the destruction of RBCs as the immune system is activated against them and they get filtered and destroyed in the spleen.
Cold type AIHA is often secondary which conditions + infections ?
Lymphoma, leukaemia, SLE
Mycoplasma, EBV, CMV and HIV
Management of AIHA ?
- Blood transfusions
- Prednisolone
- Rituximab
- Splenectomy
What is alloimmune haemolytic anaemia + what are the two scenarios where this occurs ?
It occurs when there is either foreign RBCs circulating in the pts blood causing an immune reaction that destroys those RBCs or there is a foreign antibody circulating in their blood that acts against their own RBCs and causes haemolysis.
The two scenarios where this occurs are transfusion reactions and haemolytic disease of the newborn.
What happens in a haemolytic transfusion reaction ?
RBCs are transfused into the pt. The immune system produces antibodies against antigens on those foregin RBCs. This creates an immune response that leads to destruction of those RBCs.
What happens in haemolytic disease of the newborn ?
There are antibodies that cross the placenta from the mother to the fetus. These maternal antibodies target antigens on the RBCs of the fetus. This causes destruction of the RBCs in the fetus and neonate.
What is paroxysmal nocturnal haemoglobinuria ?
A rare condition that occurs when a specific genetic mutation in the haematopoietic stem cells in the bone marrow occurs during the pts lifetime. The specific mutation results in a loss of the proteins on the surface of RBCs that inhibit the complement cascade. The loss of protection against the complement system results in activation of the complement cascade on the surface of RBCs and destruction of the RBCs.
Presentation of paroxysmal nocturnal haemoglobinuria ?
The characteristic presentation is red urine in the morning containing haemoglobin and haemosiderin. The pt becomes anaemic due to the haemolysis. They are also predisposed to thrombosis (e.g. DVT, PE and hepatic vein thrombosis) and smooth muscle dystonia (e.g. oesophageal spasm and erectile dysfunction)
Management of paroxysmal nocturnal haemoglobinuria ?
With eculizumab or bone marrow transplantation. Eculizumab is a monoclonal antibody that targets complement component 5 (C5) causing suppression of the complement system. Bone marrow transplantation can be curative.
What is microangiopathic haemolytic anaemia (MAHA) ?
It is where the small blood vessels have structural abnormalities that cause haemolysis of the blood cells travelling through them. Imagine a mesh inside the small blood vessels shredding the RBCs.
MAHA is usually secondary to an underlying condition such as ?
- HUS
- DIC
- TTP
- SLE
- Cancer
Haemolytic anaemia is a key complication of prosthetic heart valves. It occurs in both bioprosthetic and metallic valve replacement. Basically the valve churns up the cells and they break down. What does the management involve ?
- Monitoring
- Oral iron
- Blood transfusions if severe
- Revision surgery may be required in severe cases
What is thalassaemia ?
It is related to a genetic defect in the protein chains that make up haemoglobin. Normally haemoglobin consists of 2 alpha and 2 beta globin chains. Defects in alpha globin chains lead to alpha thalassaemia. Defects in the beta globin chains lead to beta thalassaemia. Both conditions are AR. The overall effect is varying degress of anaemia dependant on the type and mutation
Why does thalassaemia result in splenomegaly ?
In thalassaemia the RBCs are more fragile and break down more easily. The spleen acts as a sieve to filter the blood and remove older blood cells. In thalassaemia the spleen collects all the destroyed RBCs resulting in splenomegaly.
Why does thalassaemia cause a susceptibility to fractures and prominent features such as a pronounced forehead and malar eminences (cheek bones) ?
The bone marrow expands to produce extra RBCs to compensate for the chronic anaemia.
Potential signs and symptoms of thalassaemia ?
- Microcytic anaemia (low mean corpuscular volume)
- Fatigue
- Pallor
- Jaundice
- Gallstones
- Splenomegaly
- Poor growth and development
- Pronounced forehead and malar eminences
Diagnosis of thalassaemia ?
- FBC shows microcytic anaemia
- Haemoglobin electrophoresis is used to diagnose globin abnormalities
- DNA testing can be used to look for the genetic abnormality
Note: Pregnant women in the UK are offered a screening test for thalassaemia at booking.
Why does iron overload occur in thalassaemia, how is it checked and how is it managed?
As a result of faulty creation of RBCs, recurrent transfusions and increased absorption of iron in response to the anaemia.
Pts have their serum ferritin level monitored.
Management involves limiting transfusions and iron chelation.
Effects of iron overload in thalassaemia ?
Similar to haemochromatosis:
- Fatigue
- Liver cirrhosis
- Infertility and impotence
- Heart failure
- Arthritis
- Diabetes
- Osteoporosis and joint pain
What is alpha-thalassaemia caused by + which chromosome is this coding error on ?
Defects in the alpha globin chains. Chromosome 16.