The Role Of The Haematology Laboratory Biology Essay

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Haematology is in essence 'the study of blood, its component proteins and blood cells… by observing the reactions in samples of whole blood or plasma when they are mixed with certain reagents' (Pitt and Cunningham 2009). Haematology is broken down into three sections: haematology, haemostasis and blood transfusion. Within a haematology laboratory, accuracy is vitally important: lives depend on whether the professional's diagnosis. Firstly, the blood is screened to discover if there are any abnormalities with the blood cells. Then, depending on the results, the disease type would have to be specified. For example, if anaemia was discovered, then the type and cause would need to be discovered. This would help doctors select the necessary treatment for the patient (NHS Factsheet 2009).

Antithrombin Activity

Heinz Bodies

APC resistance

Heparin Assay (Anti-Xa)

APTT ratio - Therapeutic Heparin Ratio

INR

B12/Vitamin B12

Leucocyte Alkaline Phosphatase

Bleeding Time

Lupus Anticoagulant

Bone Marrow Aspiration

Malarial Parasites

Chromosome Studies for Haematological Investigation

Plasma Viscosity

Coagulation factor assays

Platelet Function Studies

Coagulation screen

Protein C

D.Dimers

Protein S

Erythrocyte Sedimentation Rate

Prothrombin Gene Mutation

Factor V Leiden

Pyruvate Kinase, red cell

Fibrinogen

Red cell mass/plasma volume estimation

Folate

Red cell osmotic fragility

Full Blood Count

Reticulocytes

Glandular Fever Screen

Schilling Test

Haemoglobinapothy Screen

Thrombin Time

Haemosiderin

Thrombophillia Screen

Table 1: Haematology Tests: Brighton & Sussex University Hospitals (NHS Trust)

One disease which can be diagnosed within the haematology laboratory is malaria. Malaria is a parasitic disease which is transmitted by night-biting mosquitoes. In the UK, there are 'approximately 1,500 cases of malaria every year. In 2008, there were 1,370 cases and six deaths in the UK' (NHS Choices, 2010). 'Worldwide however, there were 243 million cases and nearly one million deaths' (World Health Organisation, 2009).

'In order for a sample for malaria to be diagnosed, a blood sample should be taken, usually at a hospital, rather than at the GPs surgery. A small volume is taken' (NHS Choices - Malaria Diagnosis 2009). The patient discusses where they have been - such as on a safari holiday or any stopovers where malaria is a prominent disease - and also whether they have being taken any anti-malarial medication whilst being on their travels. With this information, it can be perceived that the most likely cause of this type of malaria is Plasmodium falciparum, which have chloroquine-resistant strains (Pitt and Cunningham, 2009).

Using the blood sample taken, a thick film is made. To make the thick film, a small drop of the sample is placed on the centre of the film and spreading it out with a corner of another slide to four times its original area. The correct thickness for a thick film will be that, with the slide placed on a newspaper, small print is just visible. The film must be allowed to dry for 30 minutes at 37°C before attempting to stain it. If the procedure has to be done at a faster pace, the slide can be left near a light bulb (where the temperature reaches 50-60°C) for about seven minutes. It is imperative that it is not touched and no stain placed on the film whilst still fresh because the stain can wash the film away (Bain and Lewis 2001).

Field's Stain is the quickest and most satisfactory for thick stains.

Stain A = polychromed methylene blue; Stain B = eosin

Method of Staining

Fix the film for 10-15s in methanol. Pour off the methanol and drop on the slide 12 drops of diluted Stain B (1 volume of stain to 4 volumes of water). Immediately, add 12 drops of Stain A. Agitate the slide to mix the stains. After 1 minute rinse the slide in water, then differentiate the film for 5 seconds in phosphate buffer at pH 6.6, wash the slide in water and then place it on end to drain and dry.

Preparation of Field's Stain

Dip the slide with the dried but otherwise unfixed film on it into Stain A for 3 seconds

Dip into a jar of tap water for 3 seconds with gentle agitation

Dip into Stain B

Wash gently in tap water for a few seconds until all excess stain is removed

Drain the slide vertically and leave to dry. Do not blot.

Figure 1: Method of Staining (Bain & Lewis 2001) and;

Preparation of Field's Stain (cited in Field 1940-41/1941-42)

Figure 2: Red blood cells infected with P. falciparum

Figure 3: Rapid Diagnostic Test Dipstick Card

Diagnosis of malaria may also be taken by a Rapid Diagnostic Test. This is particularly useful where facilities or expertise for microscopic analysis of blood smears does not exist. However, these are expensive compared to blood smear tests (CIPLA, 2010).

Analysis of potential malarial samples fall under six different categories, all described in the following table:

P. falciparum

P. vivax

P. ovale

P. malariae

Infected red cells

Normal size*; Maurer's clefts†

Enlarged; Schüffner's dots‡

Enlarged; oval and fimbriated; Schüffner's dots‡

Normal or microcytic; stippling not usually seen

Ring forms (early trophozoites)

Delicate; frequently 2 or more; accolé forms^; small chromatin dot

Large, thick; usually single (occasionally 2) in cell; large chromatin dot

Thick compact rings

Very small compact rings

Later trophozoites

Compact, vacuolated; sometimes 2 chromatin dots

Amoeboid; central vacuole ; light blue cytoplasm

Smaller than P. vivax; slightly amoeboid

Band across cell; deep blue cytoplasm

Schizonts

18-24 merozoites filling 2/3 of cell (usually only seen in cerebral malaria)

12-24 merozoites, irregularly arranged

8-12 merozoites filling ¾of cell

6-12 merozoites in daisy-head around central mass of pigment

Pigment

Dark to black clumped mass

Fine-granular; central mass

Coarse light brown

Dark, prominent at all stages

Gametocytes

Crescent or sausage-shaped; diffuse chromatin; single nucleus

Spherical, compact, almost fills cell; single nucleus

Oval; fills ¾ of cell; similar to, but smaller than P. vivax

Round, fills ½ to 2/3 of cell; similar to P. vivaxbut smaller, with no Schüffner's dots

Table 2: Morphological differentiation of malaria parasites (Bain and Lewis 2001)

* In P. falciparum, it is important to report the percentage of red cells that are infected

† Large, irregularly shaped, red-staining dots

‡ Fine stippling

^ i.e. marginalised to edge of cell

Treatment of malaria is the same as the anti-malaria medicine given before travelling. If diagnosis and treatment is prompt, most people make a full recovery from malaria. However, if treatment is to be successful, then treatment must start as soon as possible. 'Any medication prescribed and length of treatment depends on: the type of malaria, how bad the symptoms are, where the malaria was caught, whether anti-malaria tablets was taken, whether the patient is pregnant, and the age of the patient' (NHS Choices 2010). Once treatment has started, blood can be collected once every 24 hours and daily thereafter. This is to monitor the levels of parasite within the patient's blood. After treatment has been completed, after e.g. one month, and they seem fit and well, it may be suitable to screen their blood again to see if there is any parasite left.

Another disease which is diagnosed in the haematology laboratory is anaemia. Anaemia is 'a deficiency in the number of red blood cells or in their haemoglobin content, resulting in their pallor and lack of energy' (Collins Concise Dictionary 1989). One specific type of anaemia which is particularly common is sickle cell anaemia, which is when the shape and texture of the cell is different to normal blood cells. In sickle cell anaemia, 'the cells are hard and sticky and are shaped like crescents, which die prematurely, leading to a shortage of red blood cells' (NHS Choices 2010). Sickle cell anaemia is most commonly found in persons of African origin, however, it is found also in people from India, Greece and from Arabic regions. This type of anaemia can be diagnosed with a simple blood test.

Laboratory Features of Sickle Cell Anaemia

Haemoglobin level is 7-9g/dL, but symptoms of anaemia are usually mild

Blood film shows sickle cells, target cells and often features of splenic atrophy

Screening tests for sickling demonstrate increased turbidity of the blood after deoxygenation (e.g. with Na2HPO4). High performance liquid chromatography shows haemoglobin with an abnormal migration. In Hb SS, there is an absence of Hb A, Hb F level is usually mildly raised (5-10%)

Cranial Doppler studies can reveal flow disturbances pre-disposing to stroke

Figure 4: Laboratory Features of Sickle Cell Anaemia (Mehta and Hoffbrand 2009)

Treatment of sickle cell disease is broken down into four different objectives:

Trying to prevent sickle cell crises occurring

To provide adequate pain relief when a crisis does occur

To reduce the risk of serious complications occurring, such as infections and stroke

To treat other associated symptoms of sickle cell anaemia, such as anaemia (lack of red blood cells) or priapism (persistent and painful erection)

Figure 5: Care Plan for Patient with Sickle Cell Anaemia (NHS Choices 2010)

Treatment from a laboratory stance can include at the basic level, just the avoidance of known causes of the sickle cell anaemia, of which can include dehydration and infections. To compensate for splenic atrophy, folic acid should be given, as well as 'pneumococcal, HIB and meningococcal vaccination and oral penicillin indefinitely' (Mehta and Hoffbrand 2009). Vaso-occlusive crisis (increased sickling) can be treated with saline (if dehydrated), oxygen (if there is hypoxia) or antibiotics (for infection). More serious cases of sickle cell could result in a red cell transfusion, particularly if a stroke is predicted. Severe sickling which has resulted in a stroke, exchange transfusion will be carried out acutely to reduce Hb S levels to less than 30%. This may be important in pregnant patients and those undergoing general anaesthesia. In selected cases, stem cell transplants may be carried out.

A third disease which can be diagnosed within the haematology laboratory is leukaemia. Leukaemia is a cancer of the white blood cells. One sub-type of leukaemia is acute myeloid leukaemia (AML), which is cancer of the myeloid cells. 'Acute leukaemia is an uncommon type of cancer: each year, in England and Wales, an estimated 2,400 new cases are diagnosed. Of these cases of acute leukaemia, about 1,800 are AMLs' (NHS Choices 2010). Generally, the outlook for a patient with AML is widespread: in older patients (over-60s), the survival rate can be as low as 10-20%, whereas in younger patients, survival rates can be at 75%. According to the NHS, on average, there are 1,900 deaths due to AML. In the initial stages of diagnosis of AML, physical signs of the condition will be checked by the GP. A blood test will also be carried out:

Laboratory Features of Acute Myeloid Leukaemia:

Anaemia, thrombocytopenia and often neutropenia

Leucocytosis caused by blast cells in the blood

Infiltration of blast cells into the bone marrow (often 80-90% of marrow cells)

Raised levels of serum uric acid and lactate dehydrogenase (LD)

Cytoplasmic granules or Auer rods (condensation of granules) shown if positive by Sudan black

Figure 6: Laboratory Features of AML (Mehta and Hoffbrand 2009)

In addition to this, a bone marrow biopsy will also be carried out under a local anaesthetic whereby an area around the back of the hip bone is numbed and a sample is taken using a needle. If acute leukaemia has been diagnosed, then a lymph node biopsy may be carried out on any enlarged lymph nodes the patient may have: this is to discover how far the cancer may have spread. If it is felt that the cancer has spread to the nervous system, a sample of cerebrospinal fluid is taken.

If AML is diagnosed, then treatment usually starts within a couple of days. Treatment is broken down into two stages: an induction stage and chemotherapy. The induction stage is carried out in hospital or a specialist centre due to the fact that blood transfusions will need to take place due to the lack of healthy cells. Infection may also set in due to the patient's weakened immune system. In the chemotherapy stage of the treatment, many medicines will have to be taken, through a central line, into a vein near the heart. If the sub-type of AML is found to be acute promyelocytic leukaemia, an extra medication will be prescribed, known as all-trans retinoic acid (ATRA). This is given 'to induce differentiation; arsenic trioxide is also active in this condition' (Mehta and Hoffbrand 2009). More than 80% achieve remission in the under-60s category (where remission is defined as a return to full blood count and <5% blasts in bone marrow) with one course and >85% achieve with two courses. Older patients and those with other diseases achieve lower remission rates. Another three courses of therapy are administered to induce remission. However, in older patients, intensive chemotherapy may not be possible and may be offered supportive care on its own or one dose of palliative chemotherapy.

Overall, the role of the haematology laboratory is significant in the diagnosis and treatment of patients. As it is important for other departments to work alongside each other, it means that treatment and diagnosis can be given relatively quickly. With the diagnosis of patients advancing with new techniques now coming along thus treatments can advance.

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