Haematology Flashcards
What is the haematocrit?
Volume % of RBCs in blood
Useful when looking for polycythaemia
What is the mean corpuscular haemoglobin (MCH)?
Mean Hb quantity in RBCs - effects colour ‘chromic’
Causes of microcytic anaemia?
Iron deficiency
Thalassemia
Causes of normocytic anaemia?
Blood loss
Anaemia of chronic disease
Haemolytic anaemia
Sickle cell
Causes of macrocytic anaemia?
B12/folate deficiency (megaloblastic)
Alcohol, pregnancy, liver disease, hydroxycarbamide, hypothyroidism
What is haptoglobin?
Acute phase marker of RBC destruction. Normally binds to free Hb so may be severely reduced in haemolysis
4 drugs that cause agranulocytosis
4 'c's Carbimazole Carbemazepine Colchicine Clozapine
What is a TIBC? (Total iron binding capacity)
Looks at how many binding sites are available on transferrin.
Low - seen in Fe overload
High - seen in anaemia
What does TSAT show?
Should be about 30%
If high then Fe overload
If low then anaemia
Features of haemolytic anaemia
Increased RBC breakdown (raised BR, raised LDH, raised urobilinogen, reduced haptoglobin, pigmented gallstones)
Increased RBC production (increased reticulocytes)
3 reasons for abnormality in inherited haemolytic anaemia
Membrane defect
Enzyme abnormality
Hb abnormality
Examples of membrane problems in HA
Hereditary spherocytosis
Heridatary elliptocytosis
Examples of membrane problems in HA
G6PD deficiency
Pyruvate kinase deficiency
Hereditary spherocytosis
Disorder of spectrin
RBCs lose shape in circulation, they become rounded so harder to carry o2 - destroyed by extravascular system
Variable anaemia + jaundice
Film: spherocytes with no central pallor and small
Which condition do fava beans cause anaemia in?
G6PD deficiency
G6PD deficiency
G6PD only source of NADPH in RBC so only protection from oxidative stress
When oxidative stress (infections, fava beans, drugs) - cause anaemia + a non-spherocytic anaemia
Clinical features of G6PD deficiency
Anaemia Reticulocyte count may be high Urinalysis may show urobilinogen Elevated UC BR High LDH Low haptoglobin
Smear shows - blister + ghost cells
What are bite cells?
Seen in G6PD deficiency
Caused by the removal of Hb by the spleen
Evidence that a Heinz body has been formed then removed by the spleen
What are Heinz bodies?
Precipitated, denatured Hb. Round towards the periphery.
Seen in: G6PD deficiency, unstable Hb disorder etc
Types of acquired haemolytic anaemia
Auto-immune (warm or cold)
Allo-immune
Drug induced
Warm haemolytic anaemia
IgG ABs against RBC with max activity at 37C
RBCs get opsonised in reticuloendothelial system
Cold haemolytic anaemia
IgM ABs against RBC with max activity at 4C
IgM can bind more than 1 RBC as pentamic therefore causes clumping
Which HA is associated with IgG ABs against RBCs?
Warm
Which HA is associated with IgM ABs against RBCs?
Cold
What do you give the mum to prevent haemolytic disease of the newborn?
Anti-RhD antibodies after 1st birth if mum rhesus -ve and baby rhesus +ve
Examples of an allo-immune HA?
Haemolytic disease of the newborn
Following incompatible blood transfusion
Features of a DVT?
Unilateral leg pain Asymmetrical leg swelling Increased temperature Dilatation/distension of superficial veins Red/discoloured skin
Risk factors for a DVT
Pregnancy, cancer, COCP, major surgery, immobilisation
Wells score for DVT
Cancer Calf swelling >3cm Swollen unilateral superficial veins Tenderness along deep system Unilateral pitting oedema Bedridden >3d or surgery >12w Paralysis, paresis or recent cast Previous DVT Swelling of entire leg Other diagnosis just as likely
Investigation of a DVT
Do a wells score
If <2 then D-dimer - if positive then USS Doppler
If 2-9 - USS Doppler
Treatment of DVT
Start LMWH (enoxaparin 1.5mg/kg SC) and start warfarin. When INR is 2-3 stop LMWH and continue warfarin for 3-6m
What raises a D-dimer?
Liver disease Inflammation Malignancy Pregnancy Recent surgery
Wells score for PE
Previous DVT/PE Cancer Clinical signs of DVT Immobilisation/recent surgery Haemoptysis HR >100 Alternative diagnosis less likely
<4 = low risk - D-dimer >4 = high risk - CTPA + LMWH
What do PT and INR look at?
The extrinsic path (Factor 7)
Should be 12secs = INR of 1
Aim for INR of 2-3 if on warfarin
What does APTT look at?
Intrinsic path
Should be <40s
What does bleeding time look at?
Platelet function
What does thrombin time look at?
Fibrinogen test - time it takes to convert fibrinogen to fibrin. Tests the common path
Should be <11secs
Which is the intrinsic path?
Surface contact - 12 - 11 - 9
Which is the extrinsic path?
Tissue factor - 7
Which is the common path?
10 - (prothrombin - thrombin) - (fibrinogen - fibrin)
What are platelet type bleeds?
Involve skin + mucous membranes
What are factor type bleeds?
Involve deep tissue + joints
