The full blood examination Flashcards
1
Q
What processes are associated with low Hb?
A
Dec production: - Iron, B12, Folate - Primary BM disorder (e.g. PRCA) Increased destruction: - haemolysis - thalassaemia
2
Q
What processes are associated with low WCC?
A
Dec production:
- BM infiltration
- Primary BM disorder (e.g. MDS, agranulocytosis)
Increased destruction:
- Immune
- Drugs
- Sepsis
3
Q
What processes are associated with decreased plts?
A
Decreased production:
- Bm infiltration
- Primary BM disorder (e.g. MDS)
Increased destruction:
- Immune/ITP
- TTP
- DIC
4
Q
What processes are associated with pancytopenia?
A
Decreased production:
- BM infiltration
- Primary BM disorder (MDS, aplastic anaemia)
Increased destruction:
- Immune
- Drugs
- Sepsis
5
Q
What processes are associated with increased Hb/Polycythemia?
A
Reactive process:
- Hypoxia
- Renal disease
- Inc EPO
Clonal:
- Polycythemia vera
6
Q
What processes are associated with increased WCC?
A
Reactive:
- inflammation
- infection
Clonal:
- MPD e.g. CML, CLL
7
Q
What processes are associated with increased Plts?
A
Reactive:
- Iron deficiency
- Infection
- Inflammation
- Surgery
- Splenectomy
Clonal:
- Essential thrombocythaemia (ET)
8
Q
What processes are associated with increased eosinophils?
A
Reactive:
- vasculitis
- drugs
- parasites
- lymphoma
- malignancy
- allergy
Clonal:
- Chronic eosinophilic leukaemia (CEL)
- Hypereosinophilic syndrome
9
Q
What are common and uncommon causes of microcytic anaemia?
A
Common:
- Iron deficiency
- Thalassaemia
Uncommon:
- anaemia of chronic disease
- some myelodysplastic disorders (most macrocytic)
- sideroblastic anaemia
- hyperthyroidism
- heavy metal poisoning (e.g. lead)
10
Q
What are the 2 major causes of iron restricted erythropoiesis?
A
1) absolute iron deficiency - iron stores are absent
2) functional iron deficiency - insufficient availability of iron in the setting of normal/increased stores
- anaemia of chronic disease
- erythropoietin therapy
11
Q
What 3 factors influence Iron absorption
A
1) Hypoxia-inducible factor
- induced by reduced O2 tension
- transcriptional control of DMT-1 and ferroportin
2) Iron regulatory proteins 1 and 2 (IRP1/2s)
- respond to intracellular iron levels
- binds to iron response elements that impact upon mRNA stability and translation
3) Hepcidin
- binds to ferroportin and induces its degradation
12
Q
Causes of iron deficiency anaemia
A
Major cause in affluent countries is blood loss. GI bleeding: - gastric ulcer/gastritis - malignancy - diverticulitis Menstruation Diet (vegetarians, cows milk) Other: - coeliac disease - partial gastrectomy, bypass surgery - increased demand (pregnancy/childhood) - polycythemia rubra vera - bleeding disorders, haematuria, parasites - chronic intravascular haemolysis, haemodisderinuria - pulmonary haemosiderosis
13
Q
What findings are noted on FBC and film in IDA?
A
microcytic, hypochromic red cells
pencil cells
thrombocytosis
increased RDW
14
Q
What is found on iron studies in IDA?
A
transferrin increased TIBC increased Transferrin saturation reduced ferritin reduced soluble transferrin receptor increased
15
Q
What are usual findings in anaemia of chronic disease?
A
Normochromic, normocytic anaemia (also microcytic, hypochromic)
Inappropriately low reticulocyte count
elevated inflammatory markers
Normal to increased soluble transferrin receptor (vs increased in IDA)
16
Q
What is the mechanism of anaemia of chronic disease? (4)
A
Altered/abnormal iron homeostasis
Reduced red cell production by bone marrow
blunted response to EPO
shortened red cell survival
17
Q
What are causes of macrocytic anaemia?
A
Megaloblastic erythropoiesis:
- B12/folate deficiency
- Drugs
- MTX, pentamidine, trimethroprim
- DNA synthesis - AZA, hydroxyurea, zidovudine, various chemo
Reticulocytosis
- haemolysis
- bleeding
Others:
- BM pathology: MDS, myeloma, aplastic anaemia
- liver disease, EtOH, phenytoin
- copper deficiency, arsenic poisoning
- downs syndrome
- factitious: cold agglutinins, old sample, hyperosmolar state
18
Q
What changes in MMA and homocysteine are expected in B12 and folate deficiency?
A
Both elevated in B12 deficiency, however only homocysteine is elevated in folate deficiency.
MMA is the step pre conversion to Succinyl CoA in the mitochondria (B12 dependent)
Homocysteine is converted to methionine by both B12 and folate dependent pathways in the cytoplasm.
19
Q
What is the most common cause of B12 deficiency?
A
Pernicious anaemia
20
Q
What is the pathology of pernicious anaemia?
A
Autoimmune destruction of gastric mucosa/parietal cells.
reduced acid production and reduced IF
F>M
Associated with: blue eyes, fair hair, northern european, blood group A, thyroid disease, addison’s disease, hypoparathyroidism, hypogammaglobulinaemia, gastric carcinoma
21
Q
What are the two tests used for pernicious anaemia Dx?
A
IF antibiodies (Sn 50%, very Sp) parietal cell antibiodies, Sn but non Sp (15% normal females +ve)
22
Q
What are other causes of vitamin B12 deficiency?
A
Strict vegans
Ileal pathology - crohn’s, resection, tropical sprue, mutation/deficiency of IF, tapeworm infection
Gastrectomy
23
Q
What are clinical features of B12 deficiency?
A
Insidious onset, macrocytic anaemia
- may be severe
- pancytopenia may occur
- classically assoc with neurological disturbance
- macrocytosis may be masked by IDA or thalassaemia
Glossitis, angular stomatitis, increased melanin
Neural tube defects
Sub-acute combined degeneration of the cord
Sub-clinical deficiency
24
Q
B12 deficiency findings on blood film?
A
Macrocytic anaemia Hypersegmented neutrophils Oval macrocytes Low reticulocyte count Pancytopenia may occur
BMAT - megaloblastic
Evidence of haemolysis
25
Features of the cobalamin assay?
high values have a high negative predictive value for cobalamin deficiency.
Poorer Sp at lower levels.
Falls with pregnancy
Do not use single abn result to treat
26
Features of the holo-transcobalamin assay?
Measures small fraction of B12 bound to TCII - physiologically active.
Possibly more Sn and Sp compared to standard cobalamin assay.
27
What are part of a haemolysis screen?
Film - almost always abnormal.
Reticulocytes - elevated. RBC with RNA polychromasia on film.
DDx: haemolysis, bleeding, BM recovery.
LDH - elevated, representing increased cell turnover.
DDx: haemolysis, LPD, skeletal muscle, AMI
Haptoglobin: Decreased. Glycoprotein from liver which binds free Hb.
DDx: haemolysis, liver failure, megaloblastic anaemia, CDA, congenital
Bilirubin: elevated, unconjugated due to haem breakdown.
28
What are the clinical findings of Intravascular haemolysis and causes?
Within vessels, significantly decreased haptoglobin with positive urinary haemosiderin.
Causes: Fragmentation, PNH, Paroxysmal cold haemoglobinuria
29
What are the clinical findings of extra-vascular haemolysis and causes?
Site is within reticuloendothelial system (spleen, liver and bone marrow)
Note slight low haptoglobin with negative urinary haemosiderin.
Causes: Immune, RBC membrane defects, RBC enzyme defects, metabolic defects, bacterial and parasitic infections.
30
What are helmet cells/schistocytes associated with?
RBC fragmentation
31
What findings are associated with RBC fragmentation on a peripheral blood film?
helmet cells/schistocytes
32
What are causes of Microangiopathic haemolytic anaemia (MAHA)?
TTP: thrombotic thrombocytopenic purpura
HUS: haemolytic uraemic syndrome
PET, HELLP, Malignant hypertension, renal allograft rejection.
Atypical HUS: inherited dysregulation of complement system.
33
What are other causes of red cell fragmentation (other than MAHA)?
DIC
Mechanical haemolytic anaemia (prosthetic valves, severe valve disease)
Vascular malformations e.g. haemangiomas
Heat, venom, toxins (direct damage)
34
What is the classic pentad of TTP?
```
haemolysis with RBC fragmentation
thrombocytopenia
fever
neurological changes
renal impairment
```
35
What is the pathogenesis of TTP?
ADAMTS13 deficiency, which leads to excess vWF multimers (HMW) - abnormal platelet aggregation, followed by microvascular thrombosis and tissue ischaemia.
36
What are causes of TTP?
```
Idiopathic
Pregnancy
Drugs - cyclopsorin, chemotherapy
Bone marrow transplant
Malignancy
HIV
familial
```
37
How is a diagnosis of TTP made?
Clinical features as above
Fragmentation haemolysis with thrombocytopenia
MEDICAL EMERGENCY!
38
Management of TTP?
Plasma exchange
Avoid platelet transfusions
Immunosuppression
39
What is the somatic mutation associated with Paroxysmal Nocturnal haematuria?
pig-A
Defective production of phosphatidylinositol glycan A - fauly GPI anchor.
Loss of CD55 and CD59 proteins and thus complement mediated cell lysis, esp of red cells.
40
What is the outcome of the pathology of PNH?
intravascular haemolysis, paroxysmal.
Can lead to macroscopic haematuria, haemosiderinuria and iron deficiency.
Has increased risk of thrombosis, including the portal vein.
41
What is the gold standard of diagnosis of PNH?
flow cytometry - detection of loss of CD55 and CD59 expression from cells.
Type I = normal, Type II = medium-sn, Type III = high sensitivity.
42
What is the management of PNH?
Transfusions, supportive care, stem cell transplant.
Life long anticoagulation following 1st episode of thrombosis.
Eculizumab - anti C5 humanised chimeric monoclonal antibody- targets the terminal component of the complement cascade
= fewer transfusions and cessation of the haemoglobinuria. vulnerability to infection by encapsulated organisms.
43
What are the clinical features of paroxysmal cold haemoglobinuria?
Rare AIHA with acute intravascular haemolysis with exposure to cold.
44
What are the causes of PCH?
Idiopathic, syphilis, viral infections.
Biphasic IgG anti-P antibody (donath-landsteiner antibody) - binds RBC at low temperatures, upon warming, complement mediated lysis occurs.
45
What are findings on blood film in PCH?
Red cell agglutination
Intravascular haemolysis
Requires special lab testing
46
What is the management of PCH?
Cold avoidance
Similar to AIHA
Splenectomy not useful as predominantly intravascular haemolysis
47
In what conditions are spherocytes present?
AIHA
| Hereditary spherocytosis
48
What is the pathology of warm AIHA?
antibodies that react with blood cells at body temperature (37deg)
- IgG +/- complement components (C3d)
- RBCs taken up by macrophages in RES, via Fc receptor
49
What are causes of warm AIHA?
Idiopathic
SLE/AI disease
Lymphoproliferative disorders: CLL/lymphoma
Infection: CMV, Hep C
Drugs: methyldopa, antibiotics
Evan's syndrome - combination of autoimmune haemolysis with ITP
50
What are features of warm AIHA on film?
Anaemia, haemolysis, spherocytes, splenomegaly
51
What test is used to diagnose warm AIHA?
Direct antiglobulin test (DAT)
Demonstration of autoantibodies attached to the patient RBCs.
10% of hospital inpatients have +ve DATs.
False positives can occur if allo antibodies present from recent transfusion (delayed haemolytic transfusion reaction)
52
Transfusion in AIHA?
difficult, but can be lifesaving.
53
What is the management of AIHA?
prednisone 1mg/kg with taper
folate supplementation
other immunosuppression: AZA/mercaptopruine
Splenectomy and vaccination - after steroids, best 2nd line therapy
Rituximab - anti-CD20
54
What is the pathophysiology of cold AIHA?
Antibodies that react to RBCs
55
What are causes of cold AIHA?
Most often secondary.
- lymphoproliferative disorders
- mycoplasma
- EBV
- Autoimmune disease
Primary - CAIHA in association with MGUS or asymptomatic LPD
56
What is the management of cold AIHA?
cold avoidance, chlorambucil (underlying LPD), rituximab.
does not respond to steroids or splenectomy
57
What membrane defect is associated with hereditary spherocytosis?
Loss of vertical interactions: ankyrin (50%), spectrin (30%), band 3 (20%)
58
What membrane defect is associated with heretidary elliptocytosis?
loss of horizontal interactions.
| - alpha or beta spectrin, protein 4.1, band 3
59
What membrane defect is associated with south east asian ovalocytosis?
band 3 abnormality
60
What is the most common inherited haemolytic anaemia?
Hereditary spherocytosis
61
In what manner is hereditary spherocytosis inherited?
AD, FHx in 75%
62
How does hereditary spherocytosis present?
Haemolysis of varying intensity - exacerbated by intercurrent illness.
Jaundice, cholestasis, splenomegaly.
63
What findings are characteristic of hereditary spherocytosis on blood film?
Polychromasia, prominent spherocytes.
FBC: increased MCHC, RDW, reticulocytes.
+ve biochemical evidence of haemolysis.
DAT is generally -ve!
> typical film and family history generally enoug to make diagnosis
64
What is a sensitive test for HS?
Flow cytometry!
Detection of eosin-5-malemide binding - reacts covalently with band 3 protein.
reduced fluorescence with band 3 abnormalities.
Sn to HS, SEAO, congenital dyserythropoietic anaemia
65
What is the management of hereditary spherocytosis?
folate supplementation
| splenectomy
66
What is the mechanism of RBC damage in G6PD deficiency?
role of G6PD - production of NADPH to protect against oxidative stress, oxidation of glucose-6-phosphate.
deficiency leads to susceptibility to oxidative haemolysis
67
What are the genetic features of G6PD deficiency?
Most common RBC metabolic defect.
Gene is on X-chromosome:
hemizygous males are affected, homozygous females are affected, heterozygous females have variable manifestations - severity depends upon x inactivation
68
What are the clinical features of G6PD deficiency?
```
Hb normal between crises.
Haemolytic crises:
- rapid development of intravascular haemolysis
- bite cells/blister cells
- self limiting
```
Severe disease = chronic haemolysis.
69
What can cause false negative results on G6PD enzyme assays?
Reticulocytosis (have higher G6PD levels)
70
What is the management of G6PD crises?
stop offending agent
maintain high urine output
transfuse if severe anaemia
71
What are precipitants of G6PD crises?
```
Acute illness
Infections
Antimalarial drugs - e.g. primiquine
Sulfur containing drugs - dapsone, salazapyrin, co-trimoxazole
Aspirin
Vitamin K analogues
Napthaline
Probenecid
Amyl nitrate
Fava beans
```
72
What decreased production processes can cause thrombocytopenia?
bone marrow pathology/toxicity
| inherited platelet disorders
73
What are causes of increased destruction/consumption/sequestration of platelets?
```
ITP
Alloimmune - post transplant/infusion
Drugs
HITS
Viral infections - Hep C, HIV, CMV, EBV
DIC
TTP
Sepsis
Malaria
Snake venom
Dilutional - massive transfusion
```
74
What are the findings in ITP?
```
isolated thrombocytopenia
F>>M
may have mucocutaneous bleeding
Antibody mediated - plt destroyed in liver/spleen
Dx of exclusion
```
75
What is ITP associated with?
AIHA, CLL, Autoimmune disease (RA, SLE)
H. pylori
Hepatitis C
76
What is the management of ITP?
maintain plt high enough to prevent bleeding
Observation ok if plt >30
First line Rx is prednisone 1-2mg/kg
Then consider IVIg
If failed, splenectomy with vaccination (most effective)
Can use romiplostin/eltrombopag - TPO receptor agonist and mimetic respectively. S/c or po.
Can consider AZA, 6-MP, vincristine, rituximab or danazole
77
What are findings on investigation of DIC?
thrombocytopenia and abnormal coagulation profile:
- increased PT++, aPTT
- reduced fibrinogen
- elevated d-dimer
78
What is the mechanism of DIC?
systemic intravascular activation of the coagulation system:
- fibrin deposition/microangiopathy
- microvascular dysfunction/organ ischaemia
- consumption of platelets and coagulation proteins with increased bleeding risk
- independent predictor of mortality in patients with sepsis and severe trauma
79
What are causes of DIC?
identify and manage underlying cause:
sepsis, trauma, malignancy (carcinoma, APML, MDS), pancreatitis, obstetric (amnio embolus, abruption, HELLP), liver failure, snake venom
80
What is the management of DIC?
```
treat underlying cause
bleeding:
- platelet transfusion
- FFP (coagulation factors)
- cryoprecipitate (fibrinogen)
- replacement according to blood parameters
```
81
What is the mechanism of HIT?
IgG antibody recognising heparin-PF4 complexes.
| complexes bind to platelet surface, leading to activation and consumption via Fc receptor
82
What are the clinical features of HIT?
5-14 days post heparin.
| Platelets fall by >50%, but severe thrombocytopenia is rare (
83
What is the management of HIT?
cessation of heparin.
HIT pre-test probability score
Immunoassay to detect HIT antibody (high Sn, but low Sp)
functional assay: serotonin release assay, heparin induced platelet aggregation
84
In what instances are target cells generally seen?
haemoglobinopathies/thalassaemia
85
What are the 3 types of normal haemaglobin in adults?
HbA (ɑ2β2) main haemoglobin 97%
HbA2 (ɑ2δ2) - minor Hb 2-3%
HbF (ɑ2Ɣ2) - primary form in neonates,
86
What are the features of alpha thalassaemia?
reduced alpha globin production
- reduced HbA, A2, F
Far east, SE asia
4 alpha genes, deletions
a0 thal - deletion/inactivation of both alelles on single chromosome
a+ thal - inactivation of one allele on single chromosome
87
What are the features of beta thalassaemia?
reduced B-globin production, with reduction in HbA
Mediterranean distribution
2 B-genes, with small deletions/mutations >200
B0 - abn gene not expressed
B+ reduced expression of the abnormal gene
88
what are the features of a-thal trait?
(--/aa), (aa/a-) normal HPLC and elecrophoresis - require molecular studies to diagnose
89
what is HbH disease?
(--/-a) - chronic haemolysis, splenomegaly, HbH inclusions, HbH on HPLC, confirmed by genetic studies
90
What is hydrops faetalis?
(--/--) - incompatible with extrauterine life, Hb Barts (gamma 4 only)
91
What are the findings on FBC of B-thalassaemia trait/minor?
Reduced MCV, MCH
poikilocytosis, basophilic stippling, target cells
HPLC: increased HbA2, increased HbF
92
How can a false negative HPLC occur in b-thal trait?
iron deficiency can reduce HbA2 levels, must always check iron status
93
What is the genetics of B-thalassaemia major
Homozygous/compound heterozygotes for b-thalassamia with severe or absent b-globin production.
94
What are the clinical features of B-thalassaemia major?
dependence on transfusion to maintain life from early childhood (from 3-6 months)
erythroid marrow expansion, haemolysis, extra medullary haemopoiesis
Growth retardation, skeletal abnormalities
95
What are findings on investigation of B-thalassaemia major?
FBC Hb 30-70, MCV 50-60, MCH 12-18
Marked anisopoikilocytosis, stippling, NRBCs
HPLC elevated HbA2, HbF. Absent HbA
96
What is the management of B-thalassaemia major?
Transfusion support - aiming 90-100 Hb to suppress extra-medullary haemopoiseis and support development
Iron chelation therapy if ferritin >2500 (cardiac risk)
Aim for ferritin
97
What is the pathology of sickle cell disease?
CAG to CTG - b-globin gene
valine substituted for glutamic acid = HbS
HbS then polymerises into long fibres with low O2
distortion of erythrocyte with membrane damage.
change in rheology, leading to impaired flow, haemolysis, vaso-occlusion and increased endothelial adhesion
sickle crisis
one of the most common AR diseases.
Heterozygotes have normal haematology
98
What are features seen on a hyposplenic blood film?
```
howell jolly bodies
target cells
occasional nucleated red blood cells
acanthrocytes
lymphocytosis
```
