Category Archives: HEMATOLOGY

VENIPUNCTURE TECHNIQUE

1. Select a sterile, dry, preferably plastic syringe of the capacity required, e.g. 2.5 ml, 5 ml, or 10 ml.
Attach to it a 19 or 20 SWG needle (preferably a disposable one). If the patient is a child or adult with small veins, use a 23 SWG needle.

Note: When not using a disposable syringe or needle, check the syringe for good suction and the needle for any blockage, directing the syringe and needle safely away from the patient.
Ensure all air is expelled from the syringe.
Whenever possible use a disposable needle and syringe.

2. Apply a soft tubing tourniquet or velcro fastening arm band to the upper arm of the patient to enable the veins to be seen and felt.
Do not apply the tourniquet too tightly for longer than 2 minutes. Ask the patient to make a tight fist which will make the veins more prominent.

3. Using the index finger, feel for a suitable vein, selecting a sufficiently large straight vein that does not roll and with a direction that can be felt.
If a vein cannot be felt, apply a pressure cuff above the elbow and raise the pressure to 80 mm (deflate the cuff once the needle is in the vein).

4. Cleanse the puncture site with 70% ethanol and allow to dry. Do not re-touch the cleansed area.

5. With the thumb of the left hand holding down the skin below the puncture site, make the venepuncture with the bevel of the needle directed upwards in the line of the vein. Steadily withdraw the plunger of the syringe at the speed it is taking the vein to fill. Avoid moving the needle in vein

If the plunger is withdrawn too quickly this can cause haemolysis of the blood and the collapse of a small vein.

6. When sufficient blood has been collected, the tourniquet and instruct the patient to open his or her fist. Remove the needle and immediately press on the puncture site with a piece of dry cotton wool. Remove the tourniquet completely. Instruct the patient to continue pressing on the puncture site until the bleeding has stopped.

7. Remove the needle from the syringe and carefully fill the container(s) with the required volume of blood. Discard the needle safely.

Do not attempt to re-sheath it because this can result in needle-stick injury.
Important: Do not fill a container with the needle attached to the syringe. Forcing the blood through the needle can cause haemolysis.

8. Mix immediately the blood in an EDTA or citrate anticoagulated container. When required, make a thick blood film from the blood remaining in the syringe. Immediately label carefully all the
blood samples.

9. Check that bleeding from the venipuncture site has stopped. Cover the area with a small dressing

HOW TO COLLECT CAPILLARY BLOOD

Capillary blood can be collected from:


The ‘ring’ finger of a child or adult
Do not stick the thumb or index finger
as these are the most sensitive.

The heel of an infant up to one year old Care must be taken not to damage the heel by sticking it too near the edge or by holding it too forcibly

Make sure the puncture area is warm to allow the blood to flow freely. On cold days soak the hand or foot of an infant in warm water prior to collecting a sample.


1 Cleanse the puncture area with 70% ethanol. Allow the area to dry.

2 Using a sterile pricker or lancet, make a rapid puncture, sufficiently deep to allow the free flow of blood

3 Wipe away the first drop of blood with a dry piece of cotton wool and use the next few drops for the test. Do not squeeze too hard because this will result in an unreliable test result.

4 When sufficient blood has been collected, press a piece of dry cotton wool over the puncture area until bleeding stops.

CHRONIC LYMPHOID LEUKEMIA

  • Marked lymphocytosis
  • Smugde cells are present
  • CD 19+ and weak IgM & IgD expression
  • Normochromic normocytic anaemia Reduced concentration of serum immunoglobulins
  • Neutropenia and red cell aplasia
  • Nodullar diffuse bone marrow, high concentration of lymphocytes
  • White pulp in the skin

Clinical Features

  • Lymphadenopathy
  • Splenomegaly (less common)
  • Hepatomegaly( late stages)
  • Bruising
  • Immunosupression

Staging

  1. Lymphocytosis >5×10^9/L
  2. 1 + enlarged lymph
  3. 2 + enlarged liver and spleen
  4. 3 +anemia and splenomegaly
  5. 4 + thrombocytopenia

CHRONIC MYELOID LEUKEMIA

Arises due to Philadelphia chromosome t(22;9) The BCL- ADR oncogene

  • Marked leukocytosis with left shift (<200×10^9)
  • Normocytic normochromic anaemia
  • Increase in basophils and platelets
  • Hypercellular bone marrow (granulopoietic predominant)
  • High serum uric acid

Clinical Features

  • Hypermetabolism
  • Splenomegaly
  • Features of anaemia
  • Abnormal platelet count
  • Renal diseases
  • Rare visual disturbance, priapism

Staging

  1. Chronic phase: more than 10% blasts
  2. Accelerated phase: 15-30% blasts, 20% basophils and thrombocytopenia
  3. Blasts phase: more than 20% blasts, it is acute and respond poorly to treatment

TYPES OF ANAEMIA

Anemia classified as follows based mechanisms described here

Iron deficiency
Microcytic hypochromic RBCs
● MCHC: ↓ Below 320 g/l
● MCV: ↓ Below 78 fl
● Reticulocytes: Normal or Low
– cells with ‘pencil’ appearance

Macrocytic anaemia
Folate deficiency(megaloblastic)
-MCV: ↑ More than 100 fl
– Macrocytes mostly oval, occasional megaloblast, pancytopenia
– Reticulocytes: Normal or ↓
-(late stages), hypersegmented neutrophils. -WBC and platelets: ↓
-MCHC: Normal
Liver disease: Non-megaloblastic Macrocytes (mainly round with target cells)

Sickle cell disease – Sickle cells, polychromasia,
● HbS: Positive
poikilocytosis, nucleated red cells,
● Reticulocytes: ↑ (blue stippling in
HbS thalassaemia target cells. Macrocytes due to folate background of thick film)
deficiency (when patient not receiving
folate)
Further test: Hb electrophoresis.

MECHANISM OF ANEMIA

BLOOD LOSS
● Acute bleeding, e.g. from wounds, surgical, ectopic pregnancy, placenta praevia
● Chronic blood loss, e.g. hookworm infection, schistosomiasis, gastrointestinal bleeding, menorrhagia

DECREASED RED CELL PRODUCTION
● Lack of essential nutrients, e.g. deficiencies of iron,
folate, vitamin B12, protein
● Depressed bone marrow activity, e.g. anaemias associated with chronic disease such as tuberculosis, HIV disease, chronic nephritis, chronic hepatitis,
connective tissue disorders, malignant disease, leukaemias
● Due to drugs, chemicals, ionizing radiation, some viruses
● Thalassaemia syndromes

INCREASED RED CELL DESTRUCTION
(HAEMOLYSIS)
● Inherited haemolytic anaemias:
– Haemoglobinopathies, e.g. sickle cell diseases,
thalassaemia syndromes
– Red cell enzyme deficiencies, e.g. G6PD
deficiency, pyruvate kinase deficiency
– Red cell membrane defects e.g. hereditary
spherocytosis
● Non-immune acquired haemolytic anaemias:
– Infections, e.g. malaria, African trypanosomiasis, meningococcal septicaemia, C. perfringens
infection, bartonellosis
– Pre-eclampsia and HELLP syndrome (haemolysis, elevated liver enzymes, low platelet count)
– Conditions which cause disseminated intravascular coagulation (DIC)
– Haemolytic uraemic syndrome
– Hypersplenism and splenomegaly, e.g. visceral
leishmaniasis, hyper-reactive malaria, splenomegaly, myelofibrosis
– Burns
– Venomous snake and spider bites
– Chemicals, oxidant drugs, local herbal remedies
– Paroxysmal nocturnal haemoglobinuria
● Immune acquired haemolytic anaemias (DAT positive):
– Haemolytic disease of the newborn
– Haemolytic blood transfusion reaction
– Warm reactive autoantibody, e.g. drug-induced chronic lymphatic leukaemia, lymphoma, systemic lupus erythematosus
– Cold reactive autoantibody, e.g. M. pneumonia infection, lymphoma
– Paroxysmal cold haemoglobinuria

HAEMOGLOBIN MEASUREMENT

Haemoglobin is measured to detect Anaemia and its severity and to monitor an patient’s response to treatment. Monitoring the haemoglobin level (or PCV) is also required when patients with HIV disease are being treated with drugs such as AZT. The test is also performed to check the haemoglobin level of a blood donor prior to donating blood.

What are normal ranges for Haemoglobin?

Children at birth . . . . . . . . . 135–195 g/l
Children 2 y–5 y . . .. . . . . . 110–140 g/l
Children 6 y–12 y . . . . . . . .. . . 115–155 g/l
Adult men. . . . . . . . . . . . . . . 130–180 g/l
Adult women . . . . . . . . . . . 120–150 g/l
(Pregnant women) . . . . . . . . . . 110–138 g/l

As stated, Hb measurement along with other parameters can be used to identify different types of anaemia as described here

Hb 12 g/dl Not anaemic
Hb 10–11 g/dl Mild anaemia
Hb 8–9 g/dl Moderate anaemia
Hb 6–7 g/dl Marked anaemia
Hb 4–5 g/dl Severe anaemia
Hb 4 g/dl Critical

MEGALOBLASTIC ANEMIA

  • Hypersegmented nuclei
  • Macroovalocytes
  • Erythroid hyperplasia in bone marrow
  • Giant metamyelocytes
  • Hight bilirubin and Lactate dehydrogenase
  • Presence of Howell jolly bodies
  • Anisopoikilocytosis
  • Lack of polychromasia
  • High MCV
  • Pancytopenia

Clinical Features

  • Evidence of ineffective erythropoiesis
  • Neuropathy
  • Cognitive impairment
  • Loss of position
  • Atrophic glossitis