Haematology Flashcards
What is the most common cause of anaemia in hospitalised patients?
Anaemia of chronic
disease
(AoCD) or anaemia of inflammation.
What is the mechanism of anaemia of chronic
disease
(AoCD) or anaemia of inflammation?
Can be caused by infection, cancer, autoimmune
disease or chronic kidney disease. This results in a
functional iron deficiency, whereby adequate iron stores are present but the availability of iron for erythropoiesis is reduced. Hepcidin, a peptide produced by the liver in response to inflammatory cytokines, may be at least in part responsible for this phenomenon.
What do iron studies typically show in anaemia of chronic disease? What effect does iron supplementation have?
Typically, ferritin
is elevated and serum iron and transferrin saturation are low. Iron supplementation usually produces no improvement
(in contrast to true iron deficiency).
Common causes of microcytic anaemia?
3 common +4 rare
Iron deficiency, AoCD,
haemoglobinopathy.
Rarely: hyperthyroid,
lead poisoning, bone
marrow disorder,
acaeruloplasminaemia.
Common causes of macrocytic anaemia (8)?
Bleeding, haemolysis, megaloblastic anaemia, drugs (including alcohol), BM disorders, liver disease, hypothyroid and spurious (e.g. under filled tube).
Medications causing macrocytic anaemia aside from alcohol (5)?
hydroxycarbamide, methotrexate, azathioprine,
zidovudine, phenytoin
Spurious causes of macrocytosis (4)?
Cold agglutinins (red cells agglutinate due to an autoantibody; this will correct by warming a repeat FBC sample)
High white cell counts (e.g. acute leukaemia)
Severe hyperglycaemia
(in patient or by sampling close to an intravenous
dextrose infusion causing osmotic swelling)
Underfilled tube at venepuncture (increased concentration of EDTA anticoagulant).
What commonly differentiates macrocytic anaemia caused by alcohol from megaloblastic anaemia caused by B12/folate deficiency?
The resulting anaemia and macrocytosis are usually mild, in contrast to megaloblastic anaemia where the MCV may be as high as 120 fl.
In megaloblastic anaemia, should folate or B12 be given first?
Folic acid replacement should not be given unless the vitamin B12 level is known as by stimulating erythropoiesis, folic acid
may aggravate B12 deficiency thereby precipitating subacute
combined degeneration of the cord.
What are typical blood results suggesting haemolysis (3)?
Which may be unreliable?
Typical findings include a reduced haptoglobin, raised LDH and raised unconjugated bilirubin, but these are not fully sensitive or specific. For example, haptoglobin rises as an acute phase response and may fall in liver disease and megaloblastic anaemia and can be congenitally low.
What does a positive DCT suggest?
What can cause a false positive DCT (3)?
A positive DCT suggests autoimmune haemolysis but can also be positive in other
circumstances such as following therapeutic immunoglobulin infusion, recent stem cell or organ transplantation or alloimmunization following recent blood transfusion. Results must therefore be taken in clinical context before diagnosing haemolysis.
How does LDH differ between intravascular and extravascular haemolysis?
LDH is more markedly elevated in intravascular haemolysis compared with extravascular haemolysis.
Causes of intravascular haemolysis (7)?
ABO mismatch Malaria/bartonellosis/babesiosis C. perfringens sepsis (due to alpha toxin) DIC TTP G6PD (+oxidants) PNH
Causes of drug-induced immune haemolytic anaemia?
When may the DCT be negative?
Second- or third-generation
cephalosporins or diclofenac).
The DCT may be negative
if haemolysis is massive.
Symptoms of methaemoglobinaemia (6)
Colour of blood?
Causes (6)?
Cyanosis, headache
and fatigue, leading to arrhythmias, seizures and coma in severe cases.
Blood is characteristically a chocolate brown colour.
Nitrates (including amyl nitrate) Copper sulphate Sodium chlorate Dapsone Local anesthetic agents Nitroglycerin
