Haematology Flashcards
what is the normal level of haemoglobin and MCV in woman and men?
woman
- Hb: 120 - 165 grams/litre
- MCV: 80-100 femtolitres
Men
- Hb: 130-180 grams/litre
- MCV: 80 -100 femtolitres
what the main categories of anaemia based on size of RBC?
Microcytic - low MCV indicating small RBCs
Normocytic anaemia - normal MCV indicating noral sized RBCs
Macrocytic anaemia - large MCV indicating large RBCs
what are some causes of microcytic anaemia?
thalassaemia anaemia of chronic disease iron deficiency anaemia lead poisoning sideroblastic anaemia
what are some causes of normocytic anaemia?
acute blood loss anaemia of chronic disease aplastic anaemia haemolytic anaemia hypothyroidism
what are the causes of macrocytic anaemia?
macrocytic anaemia can be megaloblastic or normoblastic
megaloblastic anaemia is the result of impaired DNA synthesis - cause by B12 deficiency or folate deficiency
Normoblastic macrocytic anaemia is caused by
- alcohol
- reticulocytosis (usually from haemolytic anaemia or blood loss)
- hypothyroidism
- liver disease
- drugs such azathioprine
what are the general symptoms of anaemia?
tiredness shortness of breath headaches dizziness palpitations worsening of other conditions such as angina, heart failure or PVD
what are some symptoms specific to iron deficiency anaemia?
Pica describes dietary cravings for abnormal things such as dirt and can signify iron deficiency
Hair loss can indicate iron deficiency anaemia
angular stomitis
glossitis and taste disturbance
brittle nails
Koilonychia - spoon shaped nails (late sign of severe iron deficiency anaemia)
what are some general signs of anaemia?
pale skin
conjunctival pallor
tachycardia
raised respiratory rate
what are some signs of specific causes of anaemia?
Koilonychia is spoon shaped nails and can indicate iron deficiency
Angular stomitis 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, hypertension and excoriations on the skin can indicate chronic kidney disease
what investigations should you perform for anaemia?
Haemoglobin MCV B12 folate ferritin blood film
you may consider:
OGD and colonoscopy or bone marrow biopsy if there is unclear causes
what can cause macrocytosis?
> It is commonly an artefact of the testing process – particularly if the sample has been left a long time before being processed
It is also seen in hyperglycaemia
in megaloblastic anaemia, maturation of the nucleus is delayed, which causes larger RBCs
in liver disease there is accumulation of cholesterol and/or phospholipids on the cell surface which leads to larger than normal cells
what can cause VB12 deficiency?
> Insufficient dietary intake
Vegetarianism / vegansim
Malabsorption (Pernicious anaemia – accounts for 50% of cases of B12 deficiency Or lack of intrinsic factor after gastric surgery, Coeliac disease (particularly of the terminal ileum)
HIV
what can cause folic acid deficiency?
Poor diet Alcoholism Coeliac disease Inflammatory bowel disease Medication (Methotrexate, Trimethoprim, Phenytoin - Drug causes tend to only be apparent if there is a prolonged course and / or a high dose
what investigations should you perform for B12 deficiency?
- FBC (raised MCV, low haematocrit)
- Blood smear (megalocytes, hyper-segmented polymorphonucleated cells)
- Serum VB12
- reticulocyte count - low corrected reticulocyte count
- methylmalonic acid (MMA) and homocysteine - markers of VB12 tissue deficiency - will be elevated
- Intrinsic factor antibody - positive if pernicious anaemia is the cause
- antiparietal cell antibody - positive result may suggest pernicious anaemia (however this alone is not sufficient diagnosis as APC antibody may be raised in atrophic gastritis)
how is VB12 deficiency treated?
Vitamin B12 IM injections once every three months (cyanocobalamin or hydroxocobalamin)
how does vitamin B12 deficiency present?
typically presents a megaloblastic anaemia but can also present with peripheral neuropathy and neuropsychiatric complaints
how does folate deficiency usually present?
folate deficiency classically presents as a megaloblastic anaemia with the absence of neurological signs
what investigations would you perform for folate deficiency?
peripheral blood smear (macrocytic anaemia hyper-segmented neutrophils)
FBC - low Hb, elevated MCV and MCH
reticulocyte count - low
serum folate
red blood cell folate - low
serum LDH and serum unconjugated bilirubin - elevated - a sign of ineffective erythropoiesis - present in advanced anaemia
what causes pernicious anaemia?
autoimmune disease caused by antibodies to gastric parietal cells or intrinsic factor
Intrinsic factor is normally secreted by the gastric parietal cells and absorbed in the terminal ileum
B12 binds to intrinsic factor and is absorbed with it
B12 is a coenzyme that produces methionine from homocysteine – which converts folic acid into its active form
So, whenever B12 is deficient, folic acid cannot be utilised
how is folate deficiency managed?
oral folic acid
what should you do if folic acid and B12 deficiency occur together?
The B12 deficiency MUST be treated first or you can aggravate the B12 deficiency and risk causing degeneration of the spinal cord
what is the most common cause of anaemia?
iron deficiency
what can cause iron deficiency anaemia ?
malabsorption (dietary deficiency, coeliac disease, post-gastrectomy
Drugs (PPI, tetracyclines)
Blood loss - often occult blood loss (not seen) - e.g - NSAIDs causing GI blood loss, peptic ulcer disease, malignancy, oesophageal varacies, haemorrhois
Increased physiological requirements - pregnancy, infancy
what investigations should you perform for iron deficiency anaemia ?
FBC
Hb and Haematocrit - low
MCV - low
MCH - mean cell Hb mass per cell - low
MCHC - mean cell Hb concentration per cell - low
red cell distribution width - it is the coefficient of variation in RBC volume - will be greater than 14.6%
Blood smear - microcytic, hypochromic pencil red cells
reticulocyte count will be low and the bone marrow does not have sufficient iron to produce red cells
serum iron - decreased
total iron-binding capacity (TIBC) - increased
transferrin saturation - low
serum ferritin - low
coeliac serology is recommended
H-pylori testing
how is iron deficiency anaemia managed?
oral iron replacement - ferrous sulphate or ferrous gluconate
if symptomatic with cardiac compromise - red cell transfusion
what are causes of haemolytic anaemia?
Hereditary causes - can be subdivided into membrane, metabolism or Hb defects
- Membrane: hereditary spherocytosis
- metabolism: G6PD deficiency
- haemoglobinopathies: sickle cell, thalassaemia
Acquired haemolytic anaemia - can be subdivided into immune and non-immune causes
- Immune causes - autoimmune (warm/cold antibody type), alloimmune (transfusion reaction, haemolytic disease newborn), Drug (methyldopa, penicillin)
- Non-immune causes - microangiopathic haemolytic anaemia (MAHA), prosthetic cardiac valves, paroxysmal nocturnal haemoglobinuria, infectious - malaria, drug - dapsone
what is haemolytic anaemia?
it encompasses a number of conditions that result in the premature destruction of RBCs.
what are the symptoms of haemolytic anaemia?
pallor jaundice fatigue SOB dizziness splenomegaly
what investigations would you perform for haemolytic anaemia?
FBC
MCHC - mean haemoglobin concentration per cell - increased - may indicate presence of spherocytes and reticulocytes
reticulocyte count - increased - indicates appropriate bone marrow response to anaemia
peripheral blood smear - abnormal forms
unconjugated bilirubin may be elevated due to increased haem catabolism
High LDH and low haptoglobin is 90% specific to haemolytic anaemia
Urinalysis - haemoglobinuria is present in intravascular haemolysis
Direct antiglobulin test (coombs test) - identifies RBCs coated with antibody/compliment and a positive test usually indicates and immune cause
how is autoimmune haemolytic anaemia managed?
corticosteroids - prednisolone or dexamethasone
supportive care includes folic acid supplement
how is autoimmune haemolytic anaemia diagnosed?
Coombs test
if coombs test is negative it would suggest an aquired cause of haemolytic anaemia
how is autoimmune haemolytic anaemia catagorised?
Warm or cold according to what temperature the antibodies best cause haemolysis
Warm AIHA - the antibody (usually IgG) causes haemolysis best ay body temp and haemolysis tends to occur in extravascular sites (e.g. spleen).
Management options include steroids, immunosuppression, splenectomy
causes: AI disease (SLE), neoplasia (lymphoma, CLL), drugs (methyldopa)
Cold AIHA - usually IgM and causes best haemolysis and 4 degrees C. Haemolysis is mediated by complement and is more commonly intravascular. Features may include symptoms of raynaud’s and acrocyanosis.
Patients respond well to steroids
Causes: neoplasia (lymphoma), infectious (mycoplasma, EBV)
what is sideroblastic anaemia?
it is a condition where red cells fail to completely form haem, whose biosynthesis take place partly in the mitochondria. This leads to deposits of iron in the mitochondria that form a ring around the nucleus call a ring sideroblast.
It may be congenital or acquired.
*** always think of sideroblastic anaemia when there is a microcytic anaemia that is not responding to iron
what are the different causes of sideroblastic anaemia?
congenital cause: delta aminolevulinate synthase-2 deficiency
acquired causes:
- myelodysplasia
- alcohol
- lead
- anti TB meds