Heamatology
INTRODUCTION
Haematology is the study of blood with its associated abnormalities . Hematology involves counting, analyzing and recording the appearance of all three types of cells by a clinical lab scientist. The clinical lab scientist is able to predict, detect and diagnose blood diseases. The physician rely on hematology lab test results to select and monitor therapy for these disorders. The Primary role of Haematology are :
1) To detect anaemia and assist in the diagnosis of the exact type of anaemia.
2) Identification of disorders associated with abnormal proliferation of blood cell precursors e,g Leukaemia
3) Identification of inherited blood disorders e.g Haemophilia
4) Monitoring and control of patient treatment e.g Iron tablets ingestion.
BRIEF HISTORY
The History of the Science of Hematology can be traced back as far as the 16th Century with many scientists contributing in the evolution of the Science. Example of evolutionary scientific contribution includes the following :
· In 1657 Athanasius kircher described worms in the blood.
· In 1674 Anthony van leewenhoek described the appearance of RBC.
· In 1800, Giulio Bizzozero described platelets as a petites plaques
· In 1902. James Homer Wright discovered the Wright stain which open examination of blood under the microscope
BLOOD
Blood consist of plasma - a fluid medium in which erythrocytes ( RBC), Leucocytes ( WBCs) and thrombocytes ( Platelets ) are suspended. Plasma is a complex solution of proteins , salts and numerous metabolic substances .
COMPOSITION OF BLOOD
1.Whole blood . It is made of water which constitute about 90% dissolved substances. Of the remaining 10% or dissolved substances approximately 7% are plasma proteins . 3% constitute electrolytes.
2.Plasma Proteins.
These include Albumin, Globulins and Fibrinogen.
Other Substances present in plasma include :
a) Cellular Products e.g Antibodies , Enzymes , Hormones
b) Cellular waste Products e,g Urea , Uric acid
c) Gases e.g O2 , Co2 , No2
d) Electrolytes e.g Cations , Kt , Ca2++ ,Fe2+ . Anion include Bicarbonates, Sulphates. Chloride.
e) Other Substances include Fatty acid , amino acids , iodine.
3) Formed Elements : This constitute about 45% of blood volume. It consist of
- RBC which caries O2 and CO2
- WBC which acts as scavengers and immunizing agents
- Platelets which function in blood coagulation.
BLOOD PROPERTIES & CHARACTERISTICS
- Blood constitute about 8% of total body weight . An average of 5.0 -5.6 liters of blood is in a 70kg man.
- Blood is composed of cells dispersed through the liquid portion of blood i.e plasma.
- Specific gravity of blood is about 1.055 - 1.065. Specific gravity of plasma is about 1.026 and that of RBC is 1.093.
- Cells in uncoagulated and undisturbed blood settle down slowly because of small size and large surface area of RBC. The rate of Sedimentation is known as Erythrocyte Sedimentation Rate ( ESR).
-Separation of plasma from cells can be done by centrifugation in about 5 minutes at 5.000g.The longer the time of centrifugation , the more the removal of entrapped plasma from the cells.
- Blood has a high viscosity than water. Viscosity of plasma ranges from between 1.3 to 2.0. Viscosity of blood ranges between 1.5 -3.0 and that of water is 1.0.
- The Osmotic pressure of human blood is about 5.100 mmHg approximately the pressure of 0.9% Saline solution. The Osmotic Pressure is chiefly due to varying concentration of salts , waste products , sugar , protein etc.
FUNCTION OF BLOOD.
1) Respiration : Transport of O2 from the Lungs to the tissues and Co2 from the tissues to the lungs .
Hb + 2O2 HbO4
Haemoglobulin Oxygen OxyHaemoglobulin
The Oxygen carrying pigment is called Haemoglobulin and is responsible for the Red color of the Blood.
2) Nutrition : Blood conveys food nutrients ( amino acids , glucose , Vitamins, electrolytes , fatty acids from the Intestine to the Liver via the Hepatic portal vein, while fats are convey from the alimentary canal to the tissues via the lymphatics.
3) Excretion : Blood convey waste products of metabolism ( Urea , Uric acid , carbon dioxide , creatinine from tissues where they are produced for elimination via the skin , kidneys etc.
4) Regulation of Body Temperature : Blood transport heat formed in the more active tissue to other parts of the body , thereby helping to regulate body temperature.
5) Transport of Hormones : Hormones are transported by blood from Endocrine glands where they are produced to other parts of the body where they have regulatory role.
6) Buffering Action : The buffering power of Haemoglobulin helps to maintain the constancy of PH of Blood.
7) Maintenance of Osmotic Pressure : Plasma proteins exert osmotic pressure which influence the exchange of fluid between blood and tissues.
8) Clotting : Blood contain plasma and platelets which contain all the products required for blood clotting.
9) Protection : Blood contain lysine , antitoxins and antibodies which are essential for body protection.
STRUCTURE AND FUNCTION OF BLOOD CELLS
1) Red Blood Cells:
They are biconcave in shape, with a diameter of about 8 um and a thickness of about 2um, The total average volume is about 83 cubic microns. Concentration of RBC is higher in males than females. It depends on age , sex and altitude. RBC value in males is 5.2 +/- 0.3 million per cubic meters . Female RBC value is about 4.7 +/- 0.3 million per cubic meter.
Diagram :
Function of RBC
a) Contain Haemoglobulin which carries oxygen from the lungs to the tissue.
b) Contain Carbonic anhydrase enzyme which catalyze, the reaction between water and carbon dioxide.
c) Hb in the RBC acts as excellent acid /base buffer and it contributes to about 70% of the buffering power in the blood by transporting Carbon dioxide from tissue to the lungs.
NB : If the amount of circulating Hb decreases below the normal range for an individual , the a state of anemia exist.
2.) White Blood Cells
White Blood Cells are also called Leucocytes. They are divided into two major groups depending on their cytoplasmic contents namely :
1) Granulocytes : They have granules in their cytoplasm and comprise the following Neutrophils, Eosinophils , Basophils .
2) Agranulocytes : They do not contain granules in their cytoplasm and are made up of Monocytes , small and large lymphocytes.
White blood cell count in the normal adult is 4000 – 11.000 per cubic millimeters of blood. When the value is below 4.000 cells/mm3 the individual is said to suffer from Leucopenia .If the value is above 11.000 cells/mm3 of blood the person is suffering from Leucoytosis.
Granulocytes are divided into three types depending on the ability of the granules to take up certain stains.
For Example.
1) Eosinophils granules are stained to acidic red such as eosin.
2) Basophils granules are stained in blue dyes such as Methylene Blue and Haematoxylene.
3) Neutrophils are neutral in appearance and the granules are only faintly stained by both dyes.
The life span of granulocytes is about 12 hours . The nucleus is divided into lobes or segments, giving them a name polymorphonuclei Leucocytes or Polymorps. Deficiency of circulating granulocytes in blood is term Granulocytopenia.
a) NEUTROPHILS
The size is about 10-12 um in diameter . They have fine granules that are pink in color. The nucleus is divided into 2-5 lobes or more.
NB: Neutropenia is decrease number of circulating Neutrophils, While Neutrophilia is increase. Africans have lower values due to Chronic infections than Caucasians.
Function
a) Phagocytic
b) Number increase during allergic reactions
c) Granules contain Profibrinolysin which may be released at the site of fibrin deposition to dissolve the clot.
b) EOSINOPHIL
The size is about 10-12 um. The granules are larger and red or orange in color. The nucleus is usually bilobed. The granules are closely packed.
Function
a)The level of Eosinophils is reduced by hormones from the adrenal cortex and by secretion of adrenocorticotrophic hormones.
b) The granules contain digestive enzymes and the cells die when the enzymes are used up. The pus of abscesses contain large number of dead neutrophils as well as bacteria and necrotic tissues.
c) BASOPHILS
They have a diameter of about 8- 10 um. They have few but large granules. The nucleus is usually bilobed or kidney-shaped and the granules frequently obscure the nucleus.
Function
Their granules contain Histamine and Heparin
Heparin is an anticoagulant.
d) AGGRANULOCYTES
They lack granules in their cytoplasm as seen under the light microscope and their nuclei are seen as single lobes and are referred to as Mononuclear Leucocytes. They are of two types : Lymphocytes and Monocytes.
Lymphocytes are divided into two according to their size viz Large and Small Lymphocytes
a) Small Lymphocytes : They are about 7-10um in diameter. Have no granules. The nucleus is round and stain deep purple and occupies most of the cell leaving very small cytoplasm
b) Large Lymphocytes : Have a diameter of about 12-15 um. Have no granules. The nucleus is pale and has more plentiful cytoplasm than the small lymphocytes.
Lymphocytes also give rise to plasma cells. The plasma cells are derived from Beta lymphocytes. Plasma cells produce antibody that fight infection.
Lymphocytes stay a few hours in the blood vessels and find themselves in the lymph nodes where they survive for many days where some of them stay for about 100days.
e) Monocytes
They have no granules in their cytoplasm and are about 16 -22 um. The nucleus is horse-shoe or kidney shaped. They live for a few hours in blood and wander into the tissues. When they increase in size they are called macrophages, because they are highly phagocytic. They constitute the first stage of defense whenever there is an infection. In the tissues , they can survive for many days with some of them staying up to one year.
Diagrams of White Cells
Properties of White Blood Cells
1) Diapedesis : WBC can squeeze through pores even though the pores are of smaller diameter than the WBC.
2) Amoeboid Movement : The WBC enters tissues or tissue spaces by amoeboid motion at the rate of 40um per minute.
3) Chemotaxis : The number of chemical substances in the tissue causes the WBC to move towards or away from them
4) Phagocytosis ; This is the ability to engulf any foreign Organism dead or alive.
CHAPTER TWO
SAFETY IN THE HEMATOLOGY LABORATORY
INTRODUCTION
Many conditions in the Lab have the potential for causing injury to staff and damage to the building or to the community. Patient’s specimens, needles , chemicals , electrical equipments , reagents and glass wares all can be potential causes of accident or injury. There is need for safety procedures to be understood by laboratory managers and supervisors.
UNIVERSAL (STANDARD) PRECAUTIONS
In march 6, 1992 OSHA was introduced. Standard precaution require that all human blood, body fluid and tissues be treated as if they were infectious. Standard precaution applies to the infectious material : blood, semen, vaginal secretions, CSF, synovical fluid and body fluid with visible blood, any unidentified body fluid, unfixed slides, microhaematocrit clay and saliva from dental procedure.
Blood borne pathogen may be contain in these specimens. Pathogens may include, Hepatitis A B ,C , HIV etc.
APPLICABLE SAFETY STANDARD
- Hand washing is one of the most important safety practices ,hands must be washed with soap and water – procedure for hand washing should be observed
- Eating, drinking, smoking and applying cosmetics or lip balm must be prohibited in the Lab work area.
- Hands, pens, and other formites must be kept away from worker’s mouth and all mucous membranes.
- Food and drinks, oral medication must not be kept in the same refrigerator as lab specimens or reagents.
- mouth pipetting must be prohibited
- needles and other sharp objects contaminated with blood should not be manipulated in any way.
- contaminated sharps (needles, blades, syringes, glass slides must be placed in a puncture - resistant container with universal biohazard symbol.
- procedures such as a removing caps ,when checking for costs, filling haemocytometer chambers, making slides, discarding specimens, making dilutions and pouring specimen or fluids must be performed so that splashing, spraying or production of droplets of the specimen being manipulated in is prevented.
- personal protective clothing and equipment must be provided to the worker. Example of personal protective equipment include gowns, lab coats, gloves, eye wears ( face shield, goggles, marks)
CONTAMINATION
Contamination can occur in the form of ;-
- splashes
- poor work practices
- droplets of blood on work surface.
- To prevent contamination all work surface should be cleaned at the completion of procedures, or when the bench or work area is becomes visibly contaminated
VACCINATION
Lab workers should receive HBV vaccine. Vaccine should be available to employees at any time in case of accidental exposure
TRAINING AND DOCUMENTATION
Hematologist staff should be educated on :
- Epidemiology / system of blood borne diseases
- Mode of transmission of blood borne disease
- Use of protective equipment
- Work practices
- Recognition of exposure activities
- Location of written exposure plan for the lab
WASTE MANAGEMENT
Waste from hematology lab should be disposed according to applicable regulations.
OCCUPATIONAL HAZARD
TYPES OF HAZARDS
Ø Fire hazard
Ø Chemical hazard
Ø Electrical hazard
Ø Needle puncture
Because of the numerous flammable and combustible chemicals used in the lab, fire is a potential hazard. A good fire safety / prevention plan is necessary and should consist of the following :
Ø Enforcement of a no smoking policy
Ø Installation of appropriate fire extinguishers
Ø Placement of fire extinguishers 22gm . A distinct system for marking the locations of fire extinguishers enable quick access when they are needed. Fire extinguisher should be checked monthly and maintained annually.
Ø Placement of adequate fire detection system (alarms, sprinklers)