Haemotology Flashcards
What are the important causes of anaemia (5)
- blood loss
- haemolysis
- anaemia of chronic disease
- iron deficiency anaemia
- B12 or folate deficiency
What are some transfusion thresholds
- Don’t transfuse unless patient’s cardiovascular function is compromised
- Transfuse if Hb<70
- If above 70, assess cardio-respiratory status and then decide
How can we subdivide the causes of haemolytic anaemia
Acquired vs congential
Intravascular and extravascualr
Lab features associated with haemolytic anaemia
- Anaemia (normocytic).
- Increased serum unconjugated bilirubin (and conjugated)
- Increased urine urobilinogen
- Reduced serum haptoglobin
- Increased reticulocytes
- Increase LDH
- Urine haemosiderin (in intravascular)
What is extravascular haemolysis, where does it occur and give exmaples of its causes
Immature destruction of RBC’s due to injury to red cell membrane, opsonisation of red cells or reduced deformability.
Occurs in mononuclear phagocytic cells of spleen, liver and bone marrow.
- Hereditary elliptosis
- Heridtary spherocytosis
- G6PD (can be both)
- Sickle cell
- Auto immune (but can be both)
- Thalassemia
Causes of intravascular haemolysis
Essentially it is fragmentation haemolysis. When red cells are sheared over abnormal surfaces or the vessels are small.
MAHA
- HUS
- TTP
- Malignancy
- DIC/ infection (Malaria, Clostridium)
- HELLP/ pre-eclampsia
- Malignant hypertension
- AV malformation
Abnormal surfaces
- Prosthetic heart valves, grafts, perivalvular leaks
Misc
- G6PD (which is both)
- Mismatched blood transfusion
- Immune hemolytic anaemia (autoimmune, drug, infection)
- Unstable Hb disease
- March Hemoglobinuria
- Paroxysmal nocturnal hemoglobinuria
How do you approach investigating anaemia
MCV 80-100 - Normocytic
Reticulocytes >2
- Bleeding
- Haemolysis
Reticulocytes <2
- Bone marrow mischief
MCV >100 - Macrocytic
Presence of hypersegmented neutrophils
- B12
- Folate
- Drugs (Classically phenytoin)
Absence of hypersegmented neutrophils
- Alcohol
- Liver disease
- MDS
- Toxins
MCB <80 - Microcytic
IDA
- Reduced ferritin
- Reduced transferrin saturation (because we have increased our transferrin)
Thalassemia
- Increased ferritin
- Reduced RCC (red cell count)
Anaemia of inflammation/ anaemia of chronic disease
- Increased ferritin
- Normal/ Increased transferrin saturation (becaused we have reduced our transferrin, therefore the ratio increaseas)
Explain how iron is absorbed
Two main forms of iron
Ferris/ haem iron - Fe 2+
Ferric iron/ non haem iron - Fe3+
Non heam irone from diet (NOT MEAT) arrives in Ferric form to the small intestine.
Cannot be absorbed in Ferric form, needs to be converted to Ferris form.
DMT1 (co-transporter with hydrogen) and Vitamin C ferroreductase are present on the apical surface of the enterocyte.
Vitamin C ferroreductase reduces iron to Ferris form.
Ferris iron then enters the enterocyte by DMT1, it is then oxidised back to Ferric iron.
Iron leaves the cell through the basal surface by Ferroportin. It has to be in the Ferric form in order to be transported around the body.
Hephaectin is the enzyme that does this once through the Ferroportin transporter.
Transferrin transports ion around the body, as it cant travel by itself. It binds TWO ferric irons. Normally it is 35% saturated.
Two main fates of iron.
- Erythropoiesis in bone marrow 70%
- Goes to liver to be stored as Ferritin.
Compare hereditary elliptocytosis to spherocytosis
Similar clinical and laboratory
features to hereditary spherocytosis
except for blood film
Clinically milder disorder
Defect in horizontal interactions
What is hereditary spherocytosis and how is it passed on.
Most common hereditary haemolytic anaemia in northern Europeans
Due to abnormal red cell protein
Autosomal dominant
Structure of Hb
Each hemoglobin molecule is made up of four heme groups surrounding a globin group.
Clinical manifestations of hereditary spherocytosis(4)
Jaundice fluctuates
Most patients have some
splenomegaly
Pigment gallstones common
Aplastic crises can occur if contracts parvovirus B19 infection
Treatment of hereditary spherocytosis
Splenectomy if symptomatic
anaemia, gallstones
Diagnosis of hereditary spherocytosis
(film, flow and DAT)
Film: spherocytes and reticulocutes
Flow cytometry: less eosin-5-
maleimide
DAT negative
How many types of Hb do we have and what chromosmes are they on
Normal adult blood has 3 types of
haemoglobin
A, A1 and F
A
- 2 alpha 2 beta
A1
- 2 alpha 2 delta
F
- 2 alpha
- 2 gamma
Alpha is coded for on chromosome 16 and is duplicated – 2 on each chromosome
Beta, gamma and delta occur on
chromosome 16
Describe the coagulation cascade (dont need to include degredation)
Composed of the extrinsic and intrinsic pathway which both lead onto the common pathway resulting into an organised clot.
The extrinsic pathway (PT) is activated by exposed TF and is considered the primary initating event of the clotting cascade.
7>7a
The small amount of thrombin made by the extrinsic pathway activates the intrinsic pathway which amplifies the whole clotting cascade.
APTT (intrinsic) (tenet)
12 > 12a
11 > 11a>
9 > 9a
8 > 8a
- Carried by vWF, because it increases factor 8 half life
- Factor 2 (Thrombin) release 8 from vwf
Common pathway
- 10a + cofactor 5a = 2> 2a (pothrombin to thromrbin)
- 1> 1a (fibrinogen to fibrin)
- Fibrin reinforces the platelet plug.
Calcium is involved in a few of the steps.
How do we break down a clot i.e describe fibrinolysis. and how do we switch off the clotting cascade (anti thrombotic pathway).
Fibrin broken down to fibrin degradation products including D-dimer this is done by the eznyme plasmin.
Plasminogen is converted to Plasmin by T-PA. Thrombin activates t-PA (essentially by turning off the break).
Thrombin binds to Thrombomodulin (protein on endothelial cell surface). This complex activates Protein C (and its co-factor Protein S). These work to inhibit factor 5 and 8.
Antithrombin inhibits proteases 9, 10, 2
What is our daily requirment for iron
How much do we lose
10-20mg
Men lose 0.6 mg/d of iron - in stools
Women lose twice as much due to menstruation
When do transferrin levels go up and down
Down in inflammation and infection - a way of hiding iron from bugs
Up in Iron deficiency - as a means to try to achieve homeostatis
What is transferrin saturation, when would it be increased.
The amount of iron that is bound to transferrin.
Increased in haemochromatosis and post transfusion.
What things improve absorption of iron and what reduces it
Improved by
- Vitamin C
- Ferrous Form
- Low iron stores in the body
- Low pH (changes Fe3+ to Fe2+)
Reduced by
- Tannins
- inflammation
- Calcium
- Phytic acid in cereals
- High pH (i.e pH of panc juice)
- Phosphates
- Oxalates
How do we regulate our iron levels (and what stimulates it)
Hepcidin is a peptide hormone produced by the liver, its main function is to inhibit Ferroportin. It prevents iron being released into circulation i.e it decreases plasma iron conc. It also prevents Hepcidin being absorbed.
Stimulated by
- inflammtory cytokines like IL-6
- increased plasma iron conc/ iron bound to transferrin
- LPS.
- HFE protein (made by the haemochromatosis gene).
What is G6PD (clinically, what is seen on film)
X linked disorder that makes the RBC more susceptible to oxidative stress (i.e ROS), because G6PD is the only way that RBC’s get NADPH. Makes the cell membrane susceptible to damage.
Wee see Heinz bodies as the ROS also damages the Hb denaturing it. These Heinz bodies attach to the membrane of the RBC reducing its flexibility.
The macrophages in the spleen see this Heinz body and take a “bite out of the erythrocyte”. See reticuloytsosis. See blister cells too.
Heinz bodies also damage membrane directly so we get intravascular and extravscaular haemolysis (extra vascular being from spleen macrophages)
Only older RBC’s are targeted therefore the haemolytic episode of self limiting and stops when only young RBCs are present.
What is G6PD protective against
It is protective against falciparum malaria (I.e the parasite infected RBC is also killed by the oxidative stress).
Geographic distrubtion of G6PD (and compare severities/ variants)
West African (mild)
South-East Asia (more severe)
Mediterranean, the Middle East (most severe due to much lower levels of GPPD)
G6PDA - only occurs in older RBC’s
What causes a haemolytic episode in G6PD
Exacerbated by anything that increases ROS and puts us under oxidative stress
Infections and severe acute illness (e.g DKA)
Drugs
- Antimalarias (Primaquine, chloroquine, Pam Aquino)
- Sulphonamides (TMP, co-trimox)
- Abx - Chlorampenicol, Probenicid
- Aspirin
- NSAIDS
Moth balls (naphthalene)
Fava beans
Explain the role of G6PD enzyme
Glutathione is an antioxidant that helps mop up free radicals.
To do this it needs to be in a reduced state so that it can donate an electron.
Donation of this electron leaves Glutathione in an oxidised state unable to work.
The glutathione reductase enzyme uses NADPH to give an electron to glutathione.
NADPH is now NADP+. G6PD is the enzyme that reduces NAP+ to NADPH (it uses G6P ie glucose to do this which is a very reliable energy source)
What is DIC
Widespread inflammation (and therefore endothelial damage) which causes widespread activation of the clotting cascade.
This results in inappropriate fibrin deposition and consumption of clotting factors.
Resulting in bleeding and clotting.
Biochemical features of DIC (including film)
Low platelets
Low fibrinogen
Prolonged thrombin time
High D-Dimers
+/- prolonged PT and APTT
Red cell fragmentation (schistocytes) on blood film
Causes of DIC
Infections
- Clostridium
- Malaria
- Gram negative and meningococcal sepsis
- Gram positive sepsis
- Viral infections
Malignancy
- Acute promyelocytic leukemia
- Widespread mucin secreting adenocarcinoma
Hypersensitivity
- Anaphylaxis
- ABO incompatibility
Obstetric complications
- AFE
- Preeclampsia
Misc
- Panc
- Snake bites
- Heat stroke
- Massive blood loss
Consequences of DIC
Haemolytic anaemia (deposition of fibrin within microvasculature)
Renal failure
- Thrombi in renal glomeruli
- Microinfarcts
- Bilateral renal cortical necrosis
- Oliguria
- ARF
Haemorrhagic diathesis
- Circulatory failure and shock
Circulating anticoagulant substances
- fibrinogen breakdown products
Lungs
- microthombi in alverolar capillaries
- ARDS
- Dyspnea
- Cyanosis
- Extreme resp. difficulty
Brain
- Microinfarcts
- Fresh bleeding
- Convulsions
- Coma
Adrenals
- Massive haemorhage
- waterhouse-friderichsen syndrome (seen in meningococcemia)
Placenta
- Widespread thombi
- Atrophy of cytotrophoblast and syncytiotrophoblast
What is the only cause of a short APTT
Due to a bad draw
Does DIC cause neutropenia
Neutropenia has nothing to do with DIC
WBC not consumed in the process
Factors which tend to localise and limit thrombocoagulation are
- clearance of activated prothombocoagulants
- local degradation of clotting factors
- secretion of protease inhibitors by adjacent intact endothelium
Antithrombin III
- Function
- Clinical mafiestation of deficiency
- Treatment
- deficiency causes recurrent phlebothrombosis
- antagonizes the actions of a wide spectrum of activated serum proteases
- deficiency may be successfully treated with low dose aspirin
List 5 acquired coagulation disorders
- vitamin K deficiency and warfarin overdosage
- liver disease
- inhibitors of blood coagulation
- massive transfusion
- DIC
Who gets Vit K deficiency and how do we treat it
- People who havent eaten in days (but more likely if starvation has extended for a week or 2).
- Patients with nausea, vomiting or anorexia, or those in an intensive care situation .
- Obstructive jaundice
Can be given PO, IV or IM
- Has to be given IV/IM in obstructive jaundice
- IM not always effective, may be lost in a haematoma formed in the muscle at the site of injection.
- Has to be mixed with saline if given IV and administered slowly (no faster than 1mg/min)
Is Vit K helpful in liver disease
No unless there is a component of biliary obstruction
What coags are derranged in severe liver disease as well as on CBC
- PT, INT and APTT
- Fibrinogen level may be reduced
- Thrombocytopenia common
What improves haemostasis in liver disease
FFP
What else contributes to defective haemostasis in liver disease (other than clotting cascade deficiencies)
Enhanced fibrinolysis and poor platelet function
Should you give prothrombin in people with liver disease
No (even though factors 2,9,10 are redcued)
Prothrmobin is likely to precipitate thrombosis or DIC>
Define massive transfusion
Transfusion of >one blood volume in 24 hours
Who should get FFP and blood, what ratio should you use and how do you monitor.
People requiring massive transfusion, especially those who are losing blood volumes over only a few hours.
- At least one unit of FFP should be used for every 2 units of RBCs
-Progress should be monitored with platelet count, PT and APTT at approximately every 10 units of red cells
Most common causes of DIC
- 50% with DIC are obstetric patients having complications with pregnancy
- 30% with carcinomatosis;
- the remainder are sepsis and trauma
What is the most common inhibitor of coagulation
Lupus anticoagulant
What normally causes a prolonged APTT
Factor 8 deficiency
Unlikely to be an inhibitor to coagulation factors
What coagulation test does lupus prolong
APTT (but predisposes to thrombosis rather than bleeding)
Can people with lupus anti-coagulant have operations
Yes but risk of post op VTE is increased
How much of the haem we eat is absorbable and where is it absorbed
20% absorbable
Happens in duodenum
Total body iron content for men and women
women 2mg
men 6mg
How do we store iron, how much and where is the rest
Haemosiderin
Ferritin
15-20% is stored
Found in all body tissues,
but mainly in liver, spleen, BM and skeletal tissues
What are 4 causes of IDA
- Low PO intake
- Malabsorption (spure, coeliac, gastrectomy)
- Increased demands (pregnancy, infancy)
- Chronic blood loss
- GIT: peptic ulcers, colonic cancers, haemorrhoids, hookworm disease.
- Female genital tract: menorrhagia, metrorrhagia, cancers
What do you see in the marrow of people with IDA
mild hyperplasia of normoblasts, a/w loss of sideroblasts, absence of stainable iron in reticuloendothelial cells
Clinical features of people with IDA
Depletion of essential iron-containing enzymes leading to…
Alopecia
Koilonychia
Atrophy of tongu
Atrophy of gastric mucosa
Esophageal web (plummer Vinson triad of HMA, Atrophic glossitis, oesophageal web)
One week after severe haemorrage what is the blood likely to show.. (3)
- Reticuloytes
- Polychromatic erythrocytes
- Larger than normal red cells
What disorder could a person have if they had normal INR, APTT and platelet count but were bleeding post op.
What could you use to treat it.
Haemophilia A or vonwillibrand
If the cause is due to reduced platelet function, an infusion of desmopressin may be helpful
What should you do in a pre op assessment
- Obtain a personal & FHx of bleeding & bruising, esp. with dental extractions & operative procedures, if positive
- Perform platelet count, INR & APTT and complete blood examination
- Referral to a haemotologist for special tests of haemostasis may be indicated even if the INR and APTT are normal
- if the APTT is 43 seconds (normal range 23-35secs) surgery should be postponed until the cause of the prolonged clotting time is determined.
3 things that removal of a spleen would cause (and two things it wouldnt)
- transient thrombocytosis
- an increased liability to infection
- reticulocytosis with NO effect on the red cell survival time
- NO changes to his iron metabolism
Who would benefit from a splenectomy
People with hereditary spherocytosis
What is a sign of haemolytic transfusion reaction and how do you manage it.
Capillary oozing
1.Blood for Hb, platelet count, INR & APTT should be taken immediately
- Transfusion of platelet of FFP should not await the assessment of lab results
- .If INR & APTT are normal, FFP is not indicated
- If INR and/or APTT are prolonged, estimation of fibrinogen is important
fibrinogen deficiency may be corrected by administration of cryoprecipitate.
How is haemophilia A inherited, how common is it and what factor are they deficient in.
X linked
1 in 10,000
Factor 8
How is haemophilia B inherited, how common is it and what factor are they deficient in.
X linked
1 in 30,000
Factor 9
What is considered severe haemophilia and when do they bleed
<2% i.e severe and undetectable factor 8
Spontaneous bleeding, especially into joints and muscles
What is considered moderate haemophilia A and when do they bleed
Factor 8 between 2-5
Only beed after minor trauma
What is thalassemia A
- Usually caused by gene deletions
- The clinical severity reflects how many copies have
been deleted (because we carry 4 genes in total) - 1-2 gene deletions dont generally cause anaemia.
- 3 = moderate to severe (hemoglobin H disease)
- 4 = lethal in utero
- Causes microcytosis.
- Diagnosed by haemoglobin electrophoresis ad the
presence of H-bodies in film. May need genetic
studies.
Most common form of haemophilia A (I.e what factor level) and when do they bleed
Factor 8 >5%
suffer bleeding after trauma, esp. sporting injuries, dental extractions and surgery
What is beta thalassemia
Deformed beta chain either partial or complete.
Point mutation on chromosome 11.
= reduced or absent beta chain
autosomal recessive
Beta thalassmia minor
- Heterozygous with either one absent chain or one reduced chain
Beta thalassemia intermedia.
- Two copies of reduced beta
Beta thalassemia major
- Two copies of B0
- Symptoms dont develop until 3-6 months of life as fetal Hb still present
Alpha chains accumulate = intracellular inclusions, damage cell membranes and haemolysis. Iron deposits cause secondary haemochromatosis.
Most common in Mediterranean, african and south east asian.
What is required for a reliable diagnosis of severe haemophilia A
requires assay of plasma factor VIII
Why do people with haemophilia have a normal bleeding time
Haemophiliacs usually have a normal ‘bleeding time’ test
BECAUSE
Haemophiliacs have a normal platelet aggregatory response to microvascular injury
What factor 8 level do you aim for prior to theatre in patients with haemophilia A and do you need to continue treatment post op.
60-100%
Yes for 7-10 days to avoid delayed haemorrage
Do patients with mild haemophilia require less factor 8 replacement prior to surgery when compared to people with severe
It takes as much factor VIII to raise the level from 0-100% (as in severe haemophilia) as to raise it from 7-100% (as in mild haemophilia)
therefore, for safety in surgery, mild haemophilia is as difficult to treat as severe haemophilia
How does a haemolytic transfusion reaction present
Clinically presents as fever, shock, dyspnoea, severe bleeding, back pain and may lead to jaundice, renal failure or death.
What are two common complications of transfusion reactions.
- febrile reaction:
- Possibly due to infusion of contaminating white cells
- Prevented or greatly ameliorated by including a white cell filter in the infusion line - Urticaria - due to hypersensitivity reaction to plasma proteins
How often do febrile non-haemolytic reactions occur to donor white cells
1% of all transfusions
What do we always screen donor blood products for
Hep B, C and HIV
What is the half life of neutrophils in blood
6-7 days
Does an autologous blood transfusion eliminate the infective risk of blood transfusion
No
What is the half like for factor 8 infusion
12-16 hours
What does FFP contain
Normal levels of all coagulation factors
What does prothrombin complex contain and when is it helpful to use
Contain factors II, IX, & X and are useful in vitamin K deficiency, warfarin overdose and
patients with haemophilia B
Why is ABO compatibility important
Anti-A and anti-B antibodies are regularly found in subjects whose red cells lack the corresponding antigen
Why do people become thrombocytopenic post large volumes of tranfusion
- the patient’s platelets are diluted by the transfusion
- anti-platelet antibodies may be produced by the recipient
- the platelets in store blood are non-viable
- the transfused plasma sometimes contains anti-platelet antibodies
What causes neutropenia
- Inadequate production
- Aplastic anaemia
- Infiltrative marrow disorders
- Ineffective granulopoesis (e.g megaloblastic anaemia, myelodysplastic sydnromes)
- Suppression of committed granulocytic precursors with drugs - Excessive destruction
- SLE
- Drugs (e.g. thiouracil therapy, cotrimoxazole therapy, aminopyrine, chloramphenicol, sulfonamides, phenylbutazone)
- Splenic sequestration
- increased peripheral utilization in overwhelming infections
What is eosinophilia a/w and what is it not a feature of
A/W
- Tricinella spirlis (parasitic infection)
- Hydatid disease (parasitic infection)
- Loefflers syndrome (A transient condition a/w helminth infestation
- Polyarteritis nodosa
- Systemic vasculitis
- Hodgkins and NHL
Not A/W
- Delayed type hypersensitivity
- Acute renal allograft rejection
Causes of neutrophilia
- Inflammation:
- Macrophage activation leads to IL-1 & TNF release which stimulates marrow stromal cells to release CSF = Expansion of marrow neutrophilic progenitor cell and storage pools - Increased release of mature neutrophils from BM storage pool stimulated by IL-1 & TNF
- Increased demargination of peripheral blood neutrophils
- Decreased extravasation of neutrophils into tissues
Causes of basophilia
Rare
Often indicates myeloproliferative disease, e.g. CML
Causes of monocytosis
- Chronic infections, e.g. TB, bacterial endocarditis, rickettsiosis, malaria
- Collagen vascular diseases, e.g. SLE,
- IBD, e.g. UC
Causes of lymphocytosis
Accompany monocytosis in many cases a/w chronic immunological stimulation, e.g. TB, brucellosis)
hepatitis, CMV, EBV, bordetella pertussis
6 disorders associated with AA amyloid
- Crohn’s disease
- Rheumatoid arthritis
- Scleroderma
- Dermattomyositis
- Bronchiectasis
- chronic osteomyelitis
What are the 3 major types of amyloid
AL
- Ig light chains
- Derived from plasma cells; lambda much more often than kappa
- Frequently a/w B-cell dyscrasias (e.g. multiple myeloma)
AA
- A non-immunoglobulin protein
- Synthesized in liver
- Elevated in inflammatory states
B2 amyloid protein
- Found in Alzheimer’s
- Forms core of cerebral plaques, deposits within cerebral vessel walls
- Derives from a transmembrane glycoprotein precursor (APP)
VWF##
What is localised amyloidosis a/w
- Primary
- B cell dyscrasias
- AL - Secondary/ reactive
- AA
- RA, crohn’s disease, scleroderma, dermatomyositis, bronchiectasis, chronic
osteomyelitis)
- Typically kidneys, liver, spleen, LNs, adrenals and thyroid are involved - Haemodyalsis related
- 70% on chronic haemodialysis
- Due to deposition of beta 2 microglobulin not filtered
- Deposits in joints, synovium and tendon sheaths - Hereditary forms
What is localised amyloidosis a/w
- Nodular (tumor-forming) deposits (often AL protein)
- a/w plasma cell infiltrates – - Common in…
- lung
- Larynx
- Skin
- Bladder
- Tongue
- Periorbitally
May represent localized B-cell dyscrasias - Endocrine amyloid
3 clinical manifestations of systemic amyloidosis
- Bleeding
- Proteinuria
- Parenchyma of affected organs
What is amyloidosis and how is it diagnosed
- Proteins that accumulate in tissues and organs
- Due to too much synthesis or resistance to catabolism
- Clump together become insoluble, deposited outside of cells in a variety of tissues.
- As these accumulate, they produce pressure atrophy to adjacent parenchyma
-In important tissues, they cause symptom
- In not so important tissues may be found incidentally
- Diagnose if a biopsy stain with Congo red
Why is APTT somtiimes prolonged in vWF
The aPTT is mildly prolonged in approximately 50% of patients with vWD. The prolongation is secondary to low levels of FVIII because one of the normal functions of vWF is to protect FVIII from degradation. The PT should be within reference ranges
Normal plasma iron for men and women
Men ~ 130 ug/dL (23 umol/L)
Women ~ 110 ug/dL (19 umol/L) in women
Where is iron in the body
70% in Hb
3% in myoglobin
The rest as ferritin in enterocytes and many other cells
Describe the role of the stomach in iron absorption
Very little absorption but the acidity of gastric secretions chelates iron into its ferrous form. HELPING absorption but NOT a requirement.
This is why patients post gastrectomy get IDA.
