Anaemia - approach to diagnosis Flashcards
Define anaemia
A condition in which there is a deficiency of red cells or of haemoglobin in the blood, resulting in pallor and weariness.
What are the different causes of anaemia ?
Decreased production:
Hypoproliferative – reduced amount of erythropoiesis
Maturation abnormality – erythropoiesis present but ineffective:
- Cytoplasmic defects: impaired haemoglobinisation
- Nuclear defects: impaired cell division
Increased loss or destruction of red cells:
- Bleeding
- Haemolysis
Go over the response to anaemia
If a patient is anaemia and there is a recticulocytosis what are the 2 main possible causes for the anaemia ?
Blood loss or haemolysis
What would differentiate between a haemolysis and blood loss after seeing a recticulocytosis ?
If bleeding red cells are gone (decreased), if haemolysing then increased products of red cell destruction are seen
–Increased unconjugated serum bilirubin
–Increased urinary urobilinogen
Also splenomegaly may be present in haemolysis
Go over the breakdown of RBC’s
If you suspect a haemolytic anaemia what should you do ?
Look for evidence of red cell breakdown products and a reticulocytosis - then consider a potential cause (blood film and history may help)
If there is a reduced recticulocyte count then what sort of anaemias are you thinking ?
Ones which result in:
Hypoproliferative – reduced amount of erythropoiesis
Maturation abnormality – erythropoiesis present but ineffective:
- Cytoplasmic defects: impaired haemoglobinisation
- Nuclear defects: impaired cell division
How can anaemias be classified based on MCV and MCH/blood film ?
MCV
- Microcytic
- Macrocytic
- Normocytic
Film/MCH:
- Hypochromic
- Normochromic
What are the causes of hypochromic microcytic anaemia?
- Iron deficiency - commonest by a long way
- Thalassaemia
- Some causes of anaemia of chronic disease - chronic inflammation, malignancy
- Sideroblastic anaemia
- Lead poisoning
- Pyridoxine responsive anaemias
What are the 2 most common causes of macrocytic anaemia ?
B12 and folate deficiency
What are some of the other causes of macrocytic anaemia ?
- Myelodysplasia
- Myeloma
- Aplastic anaemia
- Reticulocytosis - these cells are bigger than erythrocytes hence cause an increased MCV (may not be associated with anaemia though)
- Cold agglutinins
What are some of the casues of macrocytosis without anaemia ?
- Alcohol
- Liver disease
- Hypothyroidism
What are the potential causes of normochromic normocytic anaemia ?
Acute blood loss/early iron deficiency
Hypoproliferative (low retic):
- Chronic diseases -inflammatory, infective, malignant disorders
- Anaemia of renal failure
- Hypometabolic states (e.g. hypothyroidism)
- Marrow failure (e.g. aplasia or infiltration)
How can renal failure result in anaemia ?
Decreased EPO production from the failing kindey results in hypoprliferation of erythroblasts
What are the mechanisms in which inflammatory/chronic diseases can result in anaemia ?
- Blunted epo response by kidney
- Impaired iron availability to erythroid precursors due to increased hepcidin produced
- Inhibition of erythroid precursor proliferation and differentiation
- Reduced red cell survival - agumented haemophagocytosis
Driven by inflammatory cytokines induced by infection/malignancy/autoimmune disease dysregulation
Most chronic anaemias (>90%) are primarily the result of impaired red cell production(low retic)
A minority are due to increased red cell destruction (haemolysis) or acute bleeding(high retic)
More than one factors may be present, e.g.
- rheumatoid arthritis anaemia of chronic disease with NSAID related GI blood loss
- where iron deficiency limits erythroid marrow response to blood loss
Go over this table of the difference between iron deficiency anaemia and anaemia of chronic disease
What is the 1st line investigation following identification of hypochromic microcytic anaemia (i.e. thinking likely iron def. anaemia)?
- 1st line = measure serum ferritin
- 2nd line = other iron studies sometimes if they have co-exisiting inflammatory disease (as ferritin can be raised because of inflammation)
- Other iron studies include - Total iron-binding capacity (TIBC)/transferrin this will be high. A high TIBC reflects low iron stores. . Note that the transferrin saturation will however be low
