Haematology Flashcards
When is someone at risk of neutropenic sepsis?
When Neuts < 0.5, typically 7-14 days post chemo, and if going to be neutropenic > 7days
How should neutropenic sepsis be managed?
Antibiotics within 30 minutes, ideally with blood cultures prior
Tazocin (piperacillin-tazobactam) or cefepime
Penicillin allergic: vancomycin + ciprofloxacin
Add in metronidazole if abdo/GI cover indicated
Gentamicin if septic shock (in addition to above)
What are common organisms that cause neutropenic fevers?
60% are gram +ve: coagulase -ve Staph epidermidis, Viridans streptococci, enterococci
30% Gram -ve: E. coli, Klebsiella, Pseudomonas
When are anti-fungals indicated in neutropenia? What should be used?
If neutropenia expected to last > 7 days
OR
If persistent or recurrent fever
Need anti-mold cover: posaconazole or amphotericin B
How do BiTEs (Bispecific T-cell engagers) work?
Fusion protein of anti-CD3 and 2 specific single chain variable fragment that brings T-cell and target together
How is cytokine release syndrome managed?
First line = anti-IL6R (tocilizumab) and anti-IL6 (siltuximab)
2nd line = steroids
What is on-target off-tumour toxicity with CD19 CAR T-cells? How is it managed?
B-cell aplasia and hypogammaglobulinaemia
IVIg
How do monoclonal antibodies exert an anti haematological cancer effect?
Through antibody-dependent cellular cytotoxicity which is NK-cell mediated
What is the mechanism of action of Brentuximab?
antiCD30 found on Reed-Sternberg cells, treatment of Hodgkin lymphoma, some AMLs
What are Blinatumomab and BI 836909?
Blinatumomab =a BiTE against CD19
BI 836909 = a BiTE against BCMA (myeloma cells)
What ICI are listed for haematological malignancies?
Pembrolizumab for R/R classical Hodgkin lymphoma ineligible for autograft
What is the mechanism of action of thalidomide used for multiple myeloma?
Inhibition of angiogenesis and TNFa synthesis
What is the mechanism of action of lenalidomide and pomalidomide?
Increase IL-10 production = anti inflammatory
AND
Inhibit TNFa, IL1B and IL6 production
AND
Induce IL-2 and IFNg production = enhance T and NK cell function, inhibit Treg
Through what mechanism do platelets bind to exposed extracellular matrix?
Platelet GP1b-V-IX binds to vWF
What are the 2 functions of von Willebrand factor?
- mediating platelet adhesion
- acts as carrier protein for factor VIII
Describe the processes of platelet activation and aggregation
Adhesion of platelet trigger GPIIb-IIIa activation, resulting in irreversible binding, shape change and platelet activation
Activated GPIIb-IIIa mediates aggregation via fibrinogen and vWF.
Activation result sin calcium influx, leading to exposure of phosphatidylserine exposure on the surface and release of granule contents which recruit other platelet and trigger coagulation cascade
What is the substrate for the following platelet adhesion receptors?
GPVI
Protease activated receptors (PARs)
GPIb-V-IX
GPIIb-IIa
GPVI = collagen
Protease activated receptors (PARs) = thrombin
GPIb-V-IX = vWF
GPIIb-IIa = Fibrin
Where do the following anti-platelets have thier action?
Aspirin
Clopidogrel
Ticagrelor
Aspirin = COX1 inhibitor, prevents TXA2 generation to inhibit platelet activation
Clopidogrel = binds P2Y12R, preventing ADP-mediated platelet activation
Ticagrelor = binds P2Y12R, preventing ADP-mediated platelet activation
What are the problems with the cascade model of coagulation?
- patients with deficiencies in contact factors do not have clinical bleeding
- implies that Factor VIIa and tissue factor activation should bypass factor VIII or IX deficiency, not true
- doesn’t explain why factor XII defieciency patients have milder bleeding phenotype
What are the phases of cell based model of coagulation?
Overlapping:
1. Initiation: exposed TF binds VIIa and activates factor X and generates trace amounts of thrombin. Excess thrombin cleared by antithrombin
- Amplification: thrombin results in activation of factors XI and IX. Also activates platelets which support the assembly of factor complexes Xa (VIIIa+ IXa) and prothrombin a (XaVa)
- Propagation: thrombin burst coverts fibrinogen to fibrin and factor XIII crosslinks fibrin leading to stabilisation of clot
What coagulants does anti-thrombin act on?
Thrombin (via factor II)
X
IX
XI
XII
What coagulants does protein C and co-factor protein S act on?
Activated Va
Activated VIIIa
What is the role of thrombin and plasmin?
Thrombin converts fibrinogen to fibrin
Plasmin converts fibrin to FDP
What are the 2 enzymes that activate plasminogen into plasmin?
tPA
uPA (urokinase)
What factors does the prothrombin time test?
Tests extrinsic pathway (tissues activated = add TF, phospholipid, calcium)
Tests TF, factor VIIa
(AND common pathway = Xa, Va and II(prothrombin)
AND thrombin activation of fibrinogen)
What factors does the APTT test?
Intrinsic pathway (surface activated = add silica or eelegic acid, phospholipid, calcium)
PK (plasma kallikrein), HMWK, VIIIa, IXa, XIa, XIIa
AND common pathway = Xa, Va and II(prothrombin)
AND thrombin activation of fibrinogen
What factors does the thrombin time test?
Thrombin activation of fibrinogen to fibrin clot
What factors can cause a low thrombin time?
- dabigatran (direct inhibitor)
- heparin (indirect inhibitor)
- low thrombin levels
- low/dyfunctional fibrinogen
- FDPs (DIC)
A deficiency in the following factors will cause a change in which coagulation assays?
-TF
- II
- IIa
- Va
- VIIa
- VIIIa
- Xa
- IXa
- XIa
- XIIa
-TF = PT (extrinsic pathway)
- II (prothrombin) = PT, APTT (common pathway)
- IIa (thrombin) = thrombin time, PT, APTT
- Va = PT, APTT (common pathway)
- VIIa = PT (extrinsic pathway)
- VIIIa = APTT (intrinsic pathway)
- Xa = PT, APTT (common pathway)
- IXa = APTT (intrinsic pathway)
- XIa = APTT (intrinsic pathway)
- XIIa = APTT (intrinsic pathway)
What is the relationship between INR to factor levels?
Non-linear, so FFP does improve prolonged INR
What is the role of a mixing study for prolonged APTT?
If APTT normalises with 1:1 mixing, there is factor deficiency
If does not normalise with mixing there is likely a factor inhibitor (either non-specific such as lupus anticoagulant, or specific factor inhibitor)
What may explain the following coag assay results:
PT: N
APTT: N
TT: N
Fibrinogen: N
Platelet count: N
Normal haemostasis
Disorder of platelet function
Factor XIII deficiency
Disorder of vascular haemostasis (connective tissue disorder)
Mild coag factor deficiency
Mild von willebrand disease
Disorder of fibrinolysis
What may explain the following coag assay results:
PT: long
APTT: N
TT: N
Fibrinogen: N
Platelet count: N
Factor VII deficiency (inherited or acquired)
Warfarin
Xa inhibitors (rivaroxaban)
Mild factor II, V or X deficiency
Lupus anticoagulant
What may explain the following coag assay results:
PT: N
APTT: long
TT: N
Fibrinogen: N
Platelet count: N
Factor VIII, IX, XI, XII, PK or HMWK deficiency
Von willebrand disease
Mild factor II, V or X deficiency
Lupus anticoagulant
What may explain the following coag assay results:
PT: long
APTT: long
TT: N
Fibrinogen: N
Platelet count: N
Vitamin K deficiency
Warfarin
Factor II, V or X deficiency
Multiple factor deficiencies (Liver failure)
Combined V and VIII deficiency
What may explain the following coag assay results:
PT: long
APTT: long
TT: long
Fibrinogen: N or abnormal
Platelet count: N
Heparin
Liver disease
Fibrinogen deficiency/dysfunction
Inhibition of fibrin polymerisation
Hyperfibrinolysis
What may explain the following coag assay results:
PT: N
APTT: N
TT: N
Fibrinogen: N
Platelet count: low
Thrombocytopenia
What may explain the following coag assay results:
PT: long
APTT: long
TT: N
Fibrinogen: N or abnormal
Platelet count: low
Massive transfusion
Liver disease
What may explain the following coag assay results:
PT: long
APTT: long
TT: long
Fibrinogen: low
Platelet count: low
DIC
Acute liver disease
What is the mechanism of action of the following anticoagulants?
Warfarin
Dabigatran
Heparin
Enoxaparin
Rivaroxaban
Warfarin = vitamin K antagonist
Dabigatran = direct thrombin inhibitor
Heparin = indirect factor Xa/IIa inhibitor
Enoxaparin = indirect factor Xa/IIa inhibitor
Rivaroxaban = direct factor Xa inhibitor
What is the clearance, safety in pregnancy and breastfeeding and drug interactions of the following anticoagulants?
Warfarin
Dabigatran
Rivaroxaban
Apixaban
Warfarin
- hepatic metabolism
- safe
- CYP2C9, 3A4 and 1A2
Dabigatran:
- 80% renal
- not safe
- p-gp inhibitors (amiodarone, verapamil)
Rivaroxaban:
- 33% renal, 18% faecal
- not safe
- CYP3a4 and p-gp inhibitors
Apixaban:
- 25% renal, 56% faecal
- not safe
- CYP3a4 inhibitors
What effect does dabigatran have on the following coag assays?
PT
APTT
TT
Fibrinogen
dRVVT (lupus anticoagulant)
PT: normal or prolonged
APTT: prolonged
TT: prolonged (the most sensitive)
Fibrinogen+ low or normal
dRVVT (lupus anticoagulant) = prolonged
What effect does rivaroxaban have on the following coag assays?
PT
APTT
TT
Fibrinogen
dRVVT (lupus anticoagulant)
PT = prolonged (most sensitive)
APTT = normal or prolonged
TT = normal
Fibrinogen = normal or low
dRVVT (lupus anticoagulant) = prolonged
What effect does apixaban have on the following coag assays?
PT
APTT
TT
Fibrinogen
dRVVT (lupus anticoagulant)
PT = normal or prolonged
APTT = normal or prolonged
TT = normal
Fibrinogen normal or low
dRVVT (lupus anticoagulant) = prolonged
What is the revers of warfarin in a patient who is bleeding?
Vitamin K
Prothrombin X
What reversal agents are used for bleeding in NOACs?
Idarucizumab 5 g for dabigatran
Prothrombin X for Rivaroxaban, specific agent = adexanet alfa (not funded), Xa mimic
What are indications for extended therapeutic anticoagulation post DVT/PE and what treatment can be used?
> 2 unprovoked PE
Anti-phospholipid syndrome
Active cancer
Apixaban 5 mg BD
Rivaroxaban 20 mg OD
Warfarin aiming INR 2-3
LMWH
What anticoagulation should be used for long term prevention in unprovoked DVT/PE?
Apixaban 2.5 mg BD
Rivaroxaban 10 mg OD
Warfarin aiming INR 2-3
What is the duration of anticoagulation for a distal DVT without persisting risk?
6 weeks
What is the relationship between female sex hormones and VTE?
Increased risk
Biggest = post partum followed by pregnancy
1st/2nd gen COC (Norethisterone, levonogestrel) safer than 3rd gen and cyproterone
Depot provera highest contraceptive risk
What is the benefit of DOACs over warfarin for VTE?
Same efficacy
Lower serious bleeding rate
What anticoagulation can be used for APS?
Warfarin or LWMH
What is the pathophysiology of heparin-induced thrombocytopenia?
IgG antibodies bind PF4-heparin complexes resulting in hypercoaguable state through platelet activation
Higher risk if unfractionated heparin
What are clinical features of HIT?
Thrombocytopenia (fall 30-50% and count > 50)
Onset after heaprin given
New thrombosis or progression of thrombus
No other cause for thrombocytopenia
How is HIT managed?
If intermediate (4-5) or high (6-8) probability: stop heparin, perform testing to confirm
If low probability (0-3) can continue heparin and consider testing if missing data points
Who should undergo platelet monitoring for HIT? What monitoring is required?
All patients on unfractionated heparin
Patients on LMWH after amjor surgery or trauma
Every 2 days
What is the pathophysiology of vaccine-induced thrombocytopenia and thrombosis (VITT)?
Anti-PF4 antibodies result in FcgRIIa-dependent platelet activation, aggregation and clot formation
Is not HIT as no heparin exposure, and does not display heparin-dependence in assays
What features suggests a platelet bleeding disorder?
- skin or mucosal bleeding
- prolonged skin cuts (> 5 minutes)
- petechiae
- immediate mild bleeding after surgery
What features suggest a clotting factor disorder?
- bleeding in deep soft tissues
- often in haemarthrosis
- delayed severe bleeding after surgery
What is the inheritance pattern of haemophilia A and B?
Haemophilia A = factor VIII, X-linked recessive
Haemophilia B = factor IX, X-linked recessive
Through what mechanism can women who are carriers of haemophilia experience mild bleeding?
Turners syndrome (XO) = severe bleeding
Extreme lyonisation = random X inactivation
What prophylaxis is given for severe haemophilia A and B?
A: Factor VII every 2 days
B: factor IX every 3 days
What is the mechanism of action and indication for Emicizumab?
Humanised bispecific mAb that bridges Factor IXa and X to restore missing factor VIII
Not affected by factor VIII inhibitors
Given subcut every 4 weeks for haemophilia A with inhibitors
What is the most common inherited bleedign disorder?
Von willebrand disease
What is the inheritance pattern of von willebrand disease?
Autosomal dominant
What factors can cause a rise in von willebrand factor levels?
- Age
- African race
- Non O blood types
- lewis blood group
- adrenaline
- inflammation
- hormones (pregnancy, OCP)
What is the treatment for von willebrand disease?
1st line = desmopressin (releases stored von willebrand factor), TXA
2nd line = von willebrand factor concentrates
What are causes of microcytic anaemia?
MCV < 80
Iron deficiency
Thalassaemia
Haemoglobinopathy
Siderobalstic anaemia
What are causes of normocytic anaemia?
MCV 80-100
Decreased production:
- bone marrow failure
- chronic disease
Increased red cell loss:
- haemolysis
- acute bleeding
What are causes of macrocytic anaemia?
MCV > 100
Megalobastic:
- B12 deficient
- Folate deficient
Non-megalobalstic:
- myelodysplasia
- liver disease
- alcohol
- pregnancy
- hypothyroidism
What are features of iron deficiency anaemia on blood film?
- hypochromic
- microcytic
- target cells
- elliptocytes
How is iron stored in the body?
Absorbed in small intestine
Carried in plasma by transferrin
Used to form myoglobin and haemoglobin
Stored in ferritin by the liver
What is the role of hepcidin?
Formed in liver, blocks cellular iron export by ferroportin to regulate systemic iron
Hepcidin is down regulated in anaemia
How is fe deficiency diagnosed?
Ferritin < 30
OR
Ferritin < 100 in high inflammatory states
OR
Tsat < 20% when Ferritin > 100
What key differences do iron studies show between iron deficiency anaemia and anaemia of chronic disease?
IDA: high transferrin, low ferritin
Chronic disease: low/N transferrin, normal/high ferritin
What is the inheritance pattern of most haemoglobinopathies?
Autosomal recessive
Where are the alpha and beta haemoglobin genes and how many copies are present?
Alpha: chromosome 16, 2 copies = 4 genes inherited
Beta: chromosome 11, 1 copy = 2 genes inhertied
What are the different types of Beta-thalassemia and their phenotypes?
Beta thalaseemia minor = 1 abnormal gene = no or mild anaemia with normal or low MCV
intermedia = 2 midly abnormal genes or 1 severe = mild-mod anaemia with low MCV
Major = 2 abnormal genes = severe anaemia with low MCV
What are the different types of Alpha-thalassemia and their phenotypes?
Silent = 1 missing gene = no anaemia, normal MCV
2-gene minor = 2 missing genes, no or midl anaemia with normal or low MCV
HbH disease = 3 missing genes = moderate to severe anaemia with low MCV
Barts disease (hydrop fetalis) = 4 missing genes, death in utero
What are the different types of Sickle cell and their phenotypes?
Sickle cell trait = 1 abnormal gene = no anaemia and normal MCV
Sickle cell disease = 2 abnormal genes = mild to severe anaemia and normal or low MCV
What is the haemoglobin electrophoresis finding for Beta thalassemia trait, alpha thalassemia trait and sickle cell trait?
Beta : elevated HbA2
Alpha: normal HbA2
Sickle: elevated HbS
How should transfusion dependent thalassemia’s be managed?
- regular RBCs
- iron chelation (deferasirox, deferiprone, desferrioxamine)
- MDT input for endocrinopathies, fertility, cardiac (due to iron overload)
- rarely HSCT
- luspatercept
What are features of sickle cell disease on blood film?
Sickle cells
(Target cells an howell-jolly bodies due to hyposplenism)
What is the pathological basis of sickle cell disease?
Glu-Val substitution in beta globin gene resulting in HbS
Is less soluble and forms gelatinous network of fibrous polymers
Red cells become distorted in low pO2, bind to endothelium and result in occlusion of microvascular -> infarction
How is sickle cell managed?
- transfusion
- hydroxyurea to increase fetal haemoglobin
- staying warm
What are different causes of bone marrow failure?
Aplastic:
- idiopathic/autoimmune
- medications
- viral
- inherited (fanconi)
Infiltration:
- malignancy, haem or other
Dysfunction:
- myelodysplasia
What is the pathophysiology of anaemia of chronic disease?
Reduction in RBC production due to
- hepcidin alteration in iron metabolism (reduced GI absorption, trapping of iron in macrophages)
- inability to increase erythropoiesis
- relative decrease in EPO
What are the different mechanisms of haemolysis?
- Intrinsic:
- enzyme deficiency: PK, G6PD
- membrane defect: hereditary spherocytosis
- Hb synthesis: sickle cell disease
- Acquired: paroxysmal nocturnal haemoglobinuria - Extrinsic:
- Immune: autoimmune haemolytic anaemia
- microangiopathic: DIC, HUS (shiga toxin), prosthetic valve, HELLP, preeclampsia, TTP
- Infections: malaria, clostridium welchii
- Lead
What is the function of DAT (coombs) test?
To detect the presence of autoantibodies on the surface of red cells
What is the pathological basis for hereditary spherocytosis and how is it diagnosed?
Spectrin deficiency with variable inheritance result in loss of red cell membrane resulting in spherocytes
Differentiated from autoimmune haemolysis by negative DAT test
Diagnosed by reduced EMA fluorescence on flow cytometry
What is the pathophysiology of paroxysmal nocturnal haemoglobinuria?
Acquired somatic mutation in PIGA gene in multipotent stem cell results in inability to synthesise GPI anchor and absence of complement inhibitors on cell surface
Results in increased complement-mediated haemolysis resulting in intravascular and extravascular haemolysis
Can also have aplastic anaemia, atypical venous and arterial thrombosis, smooth muscle dystonia
Diagnosed on flow cytometry by loss of GPI-linked proteins CD59 and CD55
What blood test findings suggest haemolytic anaemia?
Raised reticulocytes
LDH raised
Bilirubin raised
Low haptoglobin
What blood film finding suggest megaloblastic anaemia?
Oval macrocytes
Hypersegmented neutrophils
Where does extravascular haemolysis occur?
In reticuloendothelial system
What are the 3 groups that cause haemolytic anaemia?
- RBC defects:
- enzyme dysfunction
- abnormal haemoglobins
- thalassemia - Loss of structural integrity of membranes and cytoskeleton
- hereditary spherocytosis
- hereditary elliptocytosis
- paroxysmal nocturnal haemoglobinuria
- immune and drug-asscoiated antibody damage - Damage by extrinsic factors:
- mechanical trauma
- microangiopathic conditions
- chemical toxins
What feature differentiates a spherocyte from a normal RBC?
Loss of the pale centre
What results in bite and blister cells?
Oxidative damage
What is the underlying principle of the EMA test for hereditary spherocytosis?
EMA binds covalently to lysine component of extracellular protein that anchors to red cell membrane
What is the most common inheritance pattern of pyruvate kinase deficiency?
Autosomal recessive
(can also be AD)
How does pyruvate kinase deficiency result in hameolysis?
Unable to generate ATP and pyruvate, which are essential for red cell membrane function
What test should be performed for suspected drug-induced haemolytic anaemia?
G6PD
What tests should be performed for suspected mechanical stress?
Red cell morphology on blood film
Exclude other causes
How is paroxysmal noctural haemoglobinuria diagnosed?
Flow cytometric analysis of erythrocyte and neutrophil GPI-linked antigens
What diagnoses are suggested by the following DAT and blood film findings:
1. positive DAT and spherocytes
2. positive DAT and red cell agglutination
3. negative DAT and spherocytes
4. negative DAT and fragmentation
5. negative DAT and bite + blister cells
- positive DAT and spherocytes
- warm autoimmune haemolytic anaemia - positive DAT and red cell agglutination
- cold autoimmune haemolytic anaemia - negative DAT and spherocytes
- PNH or hereditary spherocytosis - negative DAT and fragmentation
- microangiopathic haemolytic anaemias - negative DAT and bite + blister cells
- G6PD deficiency
What steps are involved in the direct antiglobulin test?
Sample spun down and RBCs separated from plasma
RBCs resuspended in saline
Anti-human Ig and Complement antibodies are added
Aggregate if positive
What steps are involved in the indirect antiglobulin test?
Sample spun down and RBCs separated from plasma
Plasma added to human group O RBCs, and if present autoantibodies bind
Anti-human Ig and Complement antibodies are added
Aggregate if positive
What is the pathological basis of g9PD deficiency?
X-linked inheritance (males + homozygous females)
Loss or reduction in enzyme protecting from oxidative stress (pentose phosphate pathway)
Common in Greece and Middle East
Haemolysis (with jaundice) triggered by oxidative stress: intercurrent infection, fava beans, naphthalene or oxidant drugs
What may be seen on the blood film of someone with G6PD?
Irregularly contracted cells
Small protrusion = heinz bodies (denatured Hb)
Bite cells = heinz bodies removed by spleen
Hemi-ghost red cells = Hb retracted to one side of cell
- polychromatic macrocytes
- features of hyposplenism (howell-jolly bodies = remnant DNA)
What is the appearance of warm autoimmune anaemia on blood film?
Spherocytes
Polychromatic macrocytes (bone marrow response)
Severe = nucleated RBCs, hyposplenic changes