Haematology Flashcards Preview

GP Study > Haematology > Flashcards

Flashcards in Haematology Deck (10)
Loading flashcards...
1
Q

Allergy tests

A

Skin prick test

Most commonly used test as easy to perform and inexpensive. Drops of diluted allergen are placed on the skin after which the skin is pierced using a needle. A large number of allergens can be tested in one session. Normally includes a histamine (positive) and sterile water (negative) control. A wheal will typically develop if a patient has an allergy. Can be interpreted after 15 minutes
Useful for food allergies and also pollen

Radioallergosorbent test (RAST)

Determines the amount of IgE that reacts specifically with suspected or known allergens, for example IgE to egg protein. Results are given in grades from 0 (negative) to 6 (strongly positive)

Useful for food allergies, inhaled allergens (e.g. Pollen) and wasp/bee venom

Blood tests may be used when skin prick tests are not suitable, for example if there is extensive eczema or if the patient is taking antihistamines

Skin patch testing

Useful for contact dermatitis. Around 30-40 allergens are placed on the back. Irritants may also be tested for. The patches are removed 48 hours later with the results being read by a dermatologist after a further 48 hours

2
Q

Chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is caused by a monoclonal proliferation of well-differentiated lymphocytes which are almost always B-cells (99%). It is the most common form of leukaemia seen in adults.

A

Features

often none

constitutional: anorexia, weight loss

bleeding, infections

lymphadenopathy more marked than CML

Complications

anaemia

hypogammaglobulinaemia leading to recurrent infections

warm autoimmune haemolytic anaemia in 10-15% of patients

transformation to high-grade lymphoma (Richter’s transformation)

Investigations

blood film: smudge cells (also known as smear cells)

immunophenotyping

3
Q

Chronic myeloid leukaemia

The causes of massive splenomegaly are as follows:

myelofibrosis, chronic myeloid leukaemia, visceral leishmaniasis (kala-azar), malaria, Gaucher’s syndrome
This narrows the diagnostic possibilities considerably leaving chronic myeloid leukaemia as the most likely diagnosis.

A

The Philadelphia chromosome is present in more than 95% of patients with chronic myeloid leukaemia (CML). It is due to a translocation between the long arm of chromosome 9 and 22 - t(9:22)(q34; q11). This results in part of the ABL proto-oncogene from chromosome 9 being fused with the BCR gene from chromosome 22. The resulting BCR-ABL gene codes for a fusion protein which has tyrosine kinase activity in excess of normal

Presentation (60-70 years)

anaemia: lethargy

weight loss and sweating are common

splenomegaly may be marked → abdo discomfort

an increase in granulocytes at different stages of maturation +/- thrombocytosis

decreased leukocyte alkaline phosphatase

may undergo blast transformation (AML in 80%, ALL in 20%)

Management

imatinib is now considered first-line treatment

hydroxyurea

interferon-alpha

allogenic bone marrow transplant

Imatinib

inhibitor of the tyrosine kinase associated with the BCR-ABL defect

very high response rate in chronic phase CML

4
Q

DVT

Deep vein thrombosis: diagnosis and management

A

Diagnosis
NICE published guidelines in 2012 relating to the investigation and management of deep vein thrombosis (DVT).

If a patient is suspected of having a DVT a two-level DVT Wells score should be performed:

Clinical probability simplified score

DVT likely: 2 points or more

DVT unlikely: 1 point or less

If a DVT is ‘likely’ (2 points or more)

a proximal leg vein ultrasound scan should be carried out within 4 hours and, if the result is negative, a D-dimer test

if a proximal leg vein ultrasound scan cannot be carried out within 4 hours a D-dimer test should be performed and low-molecular weight heparin administered whilst waiting for the proximal leg vein ultrasound scan (which should be performed within 24 hours)

If a DVT is ‘unlikely’ (1 point or less) perform a D-dimer test and if it is positive arrange:

a proximal leg vein ultrasound scan within 4 hours

if a proximal leg vein ultrasound scan cannot be carried out within 4 hours low-molecular weight heparin should be administered whilst waiting for the proximal leg vein ultrasound scan (which should be performed within 24 hours)

Management
Low molecular weight heparin (LMWH) or fondaparinux should be given initially after a DVT is diagnosed.

A vitamin K antagonist (i.e. warfarin) should be given within 24 hours of the diagnosis the LMWH or fondaparinux should be continued for at least 5 days or until the international normalised ratio (INR) is 2.0 or above for at least 24 hours, whichever is longer, i.e. LMWH or fondaparinux is given at the same time as warfarin until the INR is in the therapeutic range

warfarin should be continued for at least 3 months. At 3 months, NICE advise that clinicians should ‘assess the risks and benefits of extending treatment’

NICE add ‘consider extending warfarin beyond 3 months for patients with unprovoked proximal DVT if their risk of VTE recurrence is high and there is no additional risk of major bleeding’. This essentially means that if there was no obvious cause or provoking factor (surgery, trauma, significant immobility) it may imply the patient has a tendency to thrombosis and should be given treatment longer than the norm of 3 months. In practice most clinicians give 6 months of warfarin for patients with an unprovoked DVT/PE for patients with active cancer NICE recommend using LMWH for 6 months

5
Q

Haemophilia

A 17-year-old man is investigated after he bled excessively following a tooth extraction.

Plt173 * 109/l, PT 12.9 secs, APTT 84 secs

A

Haemophilia is a X-linked recessive disorder of coagulation. Up to 30% of patients have no family history of the condition. Haemophilia A is due to a deficiency of factor VIII whilst in haemophilia B (Christmas disease) there is a lack of factor IX

Features

haemoarthroses, haematomas

prolonged bleeding after surgery or trauma

Blood tests

prolonged APTT

bleeding time, thrombin time, prothrombin time normal

Up to 10-15% of patients with haemophilia A develop antibodies to factor VIII treatment.

6
Q

Hereditary spherocytosis

A

Basics

most common hereditary haemolytic anaemia in people of northern European descent

autosomal dominant defect of red blood cell cytoskeleton

the normal biconcave disc shape is replaced by a sphere-shaped red blood cell

red blood cell survival reduced as destroyed by the spleen

Presentation

failure to thrive

jaundice, gallstones

splenomegaly

aplastic crisis precipitated by parvovirus infection

degree of haemolysis variable

MCHC elevated

Diagnosis

the osmotic fragility test was previously the recommend investigation of choice. However, it is now deemed unreliable and is no longer recommended

the British Journal of Haematology (BJH) guidelines state that ‘patients with a family history of HS, typical clinical features and laboratory investigations (spherocytes, raised mean corpuscular haemoglobin concentration[MCHC], increase in reticulocytes) do not require any additional tests

if the diagnosis is equivocal the BJH recommend the cryohaemolysis test and EMA binding

for atypical presentations electrophoresis analysis of erythrocyte membranes is the method of choice

Management

folate replacement

splenectomy

7
Q

Immune thrombocytopenia (ITP) in adults

A 34-year-old female presents due to the development of a purpuric rash on the back of her legs. Her only regular medication is Microgynon 30. She also reports frequent nose bleeds and menorrhagia. A full blood count is requested:

Hb11.7 g/dl, Platelets 62 * 109/l, WCC 5.3 * 109/l

A

Immune (or idiopathic) thrombocytopenic purpura (ITP) is an immune-mediated reduction in the platelet count. Antibodies are directed against the glycoprotein IIb/IIIa or Ib-V-IX complex.

ITP can be divided into acute and chronic forms:

Acute ITP

more commonly seen in children

equal sex incidence

may follow an infection or vaccination

usually runs a self-limiting course over 1-2 weeks

Chronic ITP

more common in young/middle-aged women

tends to run a relapsing-remitting course

Evan’s syndrome

ITP in association with autoimmune haemolytic anaemia (AIHA)

8
Q

Vitamin B12 deficiency

Mr Brown is a 54-year-old man a new diagnosis of anaemia. He has no relevant past medical history. His haematinics values are as follows:

Reference Range Iron 10 g/l, Folate 2.1, Vitamin B12 150 ng/l

A

Vitamin B12 is mainly used in the body for red blood cell development and also maintenance of the nervous system. It is absorbed after binding to intrinsic factor (secreted from parietal cells in the stomach) and is actively absorbed in the terminal ileum. A small amount of vitamin B12 is passively absorbed without being bound to intrinsic factor.

Causes of vitamin B12 deficiency

pernicious anaemia: most common cause

post gastrectomy

vegan diet or a poor diet

disorders of terminal ileum (site of absorption): Crohn’s, blind-loop etc

metformin (rare)

Features of vitamin B12 deficiency

macrocytic anaemia

sore tongue and mouth

neurological symptoms

the dorsal column is usually affected first (joint position, vibration) prior to distal paraesthesia

neuropsychiatric symptoms: e.g. mood disturbances

Management

if no neurological involvement 1 mg of IM hydroxocobalamin 3 times each week for 2 weeks, then once every 3 months

if a patient is also deficient in folic acid then it is important to treat the B12 deficiency first to avoid precipitating subacute combined degeneration of the cord

9
Q

Von Willebrand’s disease

A 17-year-old man is investigated after he bled excessively following a tooth extraction. The following results are obtained:

Plt, 173 * 109/l, PT 12.9 secs, APTT 84 secs

A

Von Willebrand’s disease is the most common inherited bleeding disorder. The majority of cases are inherited in an autosomal dominant fashion* and characteristically behaves like a platelet disorder i.e. epistaxis and menorrhagia are common whilst haemoarthroses and muscle haematomas are rare

Role of von Willebrand factor

large glycoprotein which forms massive multimers up to 1,000,000 Da in size

promotes platelet adhesion to damaged endothelium

carrier molecule for factor VIII

Types

type 1: partial reduction in vWF (80% of patients)

type 2*: abnormal form of vWF

type 3**: total lack of vWF (autosomal recessive)

Investigation

prolonged bleeding time

APTT may be prolonged

factor VIII levels may be moderately reduced

defective platelet aggregation with ristocetin

Management

tranexamic acid for mild bleeding

desmopressin (DDAVP): raises levels of vWF by inducing release of vWF from Weibel-Palade bodies in endothelial cells

factor VIII concentrate

*type 2A VWD is caused by defective platelet adhesion due to decreased high molecular weight VWF multimers (i.e. the VWF protein is too small). Type 2B is characterised by a pathological increase of VWF-platelet interaction. Type 2M is caused by a decrease in VWF-platelet interaction (not related to loss of high molecular weight multimers). Type 2N is caused by abnormal binding of the VWF to Factor VIII. There is no clear correlation between symptomatic presentation and type of VWD however common themes amongst patients include excessive mucocutaneous bleeding, bruising in the absence of trauma and menorrhagia in females.

**type 3 von Willebrand’s disease (most severe form) is inherited as an autosomal recessive trait. Around 80% of patients have type 1 disease

10
Q
A