Major Branches of Pathology

PATHOLOGY

Pathology is the branch of medicine dealing with the structure or functional changes in tissues or organs in the body, which cause or are caused by disease. MAJOR BRANCHES OF PATHOLOGY

Haematology The study of the blood. The nature, function and diseases of blood The study of the minute structure, composition and function of the Histology body tissues Immunology The study of immunity and the body's defense mechanisms The microscopic study of the form and functions of the cells of the Cytology body. Biochemistry The chemical composition of the blood and body matter Microbiology The study of microorganisms and their effect. Bacteriology The study of bacteria. Serology The study of serum - the clear portion of any body fluid Clinical Pathology Use of laboratory methods in diagnosis The pathology of disease which is surgically accessible for Surgical pathology diagnosis or disease

COLLECTION OF SPECIMENS

Aspiration Drawing off of fluid from a body cavity by means of suction (Papanicolaou smear) a smear test to detect disease of the uterine Pap smear cervix Venepuncture Puncture of a vein to withdraw a specimen of blood Removal of some tissue or organ for examination to establish a Biopsy diagnosis Swab A gauze coated stick used to take bacterial specimens Faecal fat Analysing faeces for fat content.

EXAMINATION

the growth of microorganisms in special media and the test of Culture and sensitivity these specimens' sensitivity or reaction to agents especially antibiotics Microscopic the appearance of organisms or tissue under magnification appearance Blood count number of blood cells in a given sample of blood !n vitro in a glass - observations made outside the body Autopsy examination of a body after death In vivo observation made within the living body ABBREVIATION

C&S culture and sensitivity Chol cholesterol MS mid stream urinalysis BUN blood urea nitrogen U GTT glucose tolerance test Ua urinalysis LFT liver function test ESR erthyrocyte sedimentation rate LP lumbar puncture FBS fasting blood sugar

Pathology results include reports on samples of:  Blood  Sputum  Body tissue (histology)  Semen  Cerebrospinal fluid (CSF) - the fluid that flows through the brain and spinal cord

The following figure shows a routine pathology test result. This is an analysis of a sputum specimen.

LEAVE THIS SPACE TO STICK IN A REPORT Follow the numbered parts of the report:

1. This is the patient identification, name, date of birth and address

2. This is date and the time the specimen was collected. Specimens are labelled with the patient's name and date of birth, and the date and time collected. The time can be a crucial element in analysis of body specimens as they can deteriorate quickly and produce false results.

3. This identifies the doctor who signed the pathology request. The laboratory reference number is the specimen's identification at the pathology laboratory.

4. This is the pathology centre's identification and phone number

5. This section is for the doctor to fill. It indicates whether the report needs further action or not

6. The microbiological examination indicates what the sample looked like under the microscope.

The specimen type is sputum, and 'mucopurulent' describes how it appeared (muco is a root for mucus, purulent means it contains pus)

 'Upper' refers to the part of the respiratory system it was obtained from. This sample has been coughed up by the patient and therefore has come from the upper portion of the lungs. A lower respiratory sample would have to be obtained using a bronchoscope or by induction. Induction is where a patient is given a substance to breathe (usually a salty mist) and this causes them to cough up secretions from their lungs.  `Gram stain' is a procedure where the sample is stained with different dyes, and microorganisms in the sample can then be identified by their ability to take up different colours.  `Leucocytes' are white blood cells, which help fight infection  `Gram negative cocci' are a group of bacteria cells  `Normal flora' refers to the bacteria that occur naturally in the body and normally do not cause disease  `Moderate' means there are moderate number of these cells. Pathology uses the following terms to describe quantity: scant (small), moderate, or profuse (much higher than normal) in number.

`Culture' is a substance that the sample is placed on to grow bacteria. These bacteria are then tested with different antibiotics to see what they are sensitive to.

The culture of this specimen has grown:

• Profuse Moraxella (Branhamella) catarrhalis - a large number of bacteria that, although it normally occurs in the upper respiratory tract, can cause respiratory disease if present in large numbers. • Profuse normal flora - a large amount of normal bacteria 1. The Moraxella bacteria have been exposed to different antibiotics and are shown to be resistant to some (which means these antibiotics will not kill the bacteria) but sensitive to others. The doctor can now prescribe antibiotics that will control the bacteria. 2. Microscopy means using a microscope to examine a sample at a high magnification. A laboratory technician has counted specific cells, called eosinophils, to see how much inflammation is present in the lungs. The result, 4%, is slightly elevated (slightly above average). You would not normally be expected to understand or interpret pathology results. This example is simply to make you familiar with the layout of pathology results. You should be able to identify:

 the patient concerned,

 the doctor who has ordered the tests,

 the type of sample,

 when the sample was collected. The doctor will sign the report when the results have been examined.

Haematology and serology:

Determines the number of red and white blood cells per cubic Full blood count millimetre of blood. is one of the most commonly performed tests (FBC) and a very valuable diagnostic aid. It measures the protein iron compound in the blood that carries Haemoglobin (Hb) oxygen to the cells from lungs and carbon dioxide away from count cells to the lungs Haematocrit Measures the packed cell volume of red blood cells Prothrombin index Measures the amount of time it takes for blood to clot Blood grouping and Classifies blood then determines the compatibility between blood cross matching from a donor and the patient Is applied for venereal diseases: Serology testing for AIDS which Serology testing screens for antigens or antibodies to human immunodeficiency virus (HIV) Is 'insertion of a needle into the sternum or iliac crest to obtain samples of bone marrow for analysis, to diagnose disorders Bone Marrow involving red and white blood cells, by evaluating their aspiration appearance, numbers, and development and presence of infection. determines various -types of anaemia and blood incompatibility Coombs test in pregnant women and their foetuses erythrocyte measures the rate at which red blood cells settle in unclotted sedimentation blood indicating the presence of inflammatory diseases and rate (ESR) infections prostate specific detects the presence of a specific antigen that increases in fastingantigen blood (PSA) sugar casesshows of prostate the amount cancer of glucoseand other in prostatethe blood diseases. after a period of (FBS) level fasting glucose tolerance test when a measured amount of glucose is given to the patient (GTT) to see if there is a disorder of the sugar metabolism; a simple test for the presence of glucose is a urine test using paper strips impregnated with enzymes to determine the presence of glucose in the urine.

BIOCHEMISTRY Electrolytes and organic acids in correct quantities and balance are essential for normal metabolism and function. Electrolytes include:

* sodium * potassium * magnesium * chloride * bicarbonate * calcium

Serum enzymes are proteins found in blood serum which are produced by living cells that cause chemical reactions in organic matter. They are usually not present in large amounts, but if they are it may indicate tissue damage. For example, the presence of high levels of cardiac enzymes indicates a myocardial infarction has occurred – the higher the levels the greater the damage to the heart muscle.

Lipids are free fatty acid fractions in the blood and are stored in the body. Types of lipids include:

 Cholesterol  Fatty acids  Triglycerides

If the levels of lipids are elevated it may indicate disease, for example arteriosclerosis or increased risk of heart disease.

Urinalysis Examines the physical and chemical properties of urine Measures the amount of creatinine in urine and if elevated Creatinine test indicates kidney function disturbance Creatinine clearance Measures the rate at which the kidneys remove creatinine from the Test blood; to evaluate kidney function Can indicate presence of liver disease and also the extent of the Liver function tests damage to the liver

Histopathology and cytology

Cytology studies the formation, origin, structure, function, biochemical activity and pathology of cells. Cells may be taken from:  cerebrospinal fluid  amniotic fluid  bronchial brushings  gastric aspiration  buccal (cheek) cavity  bone marrow  cervix (PAP smear)

Histopathology or Histology - the study of tissue removed from the body to identify the presence of disease. Tissue may be obtained by:

 biopsy of a small piece of tissue  removal of part or all of an organ or part of the body.

In order to obtain a quick diagnosis, a frozen section may be completed on tissue removed at operation. Microscopic slides are prepared for tissue that has been frozen by exposure to dry ice. Surgeons will wait in the operating theatre for a diagnosis to be made from the tissue, before continuing with the procedure. The extent of the surgery will depend upon the findings

Bacteriology

Bacteria are any class of microscopic plants-including some that are disease producers-which are visible by ordinary microscopic methods. Bacteriology in medicine studies disease producing bacteria which can be found in blood, sputum, urine, spinal fluid, faeces or any body secretion.

Cultures isolate infective organisms and by growing the organism the pathologist can test various antibiotics to see which effectively destroy the organisms.

Diagnostic Test Provisional Diagnosis

Acid fast bacillus Tuberculosis Blood culture Septicaemia Bone marrow biopsy Leukaemia Cardiac enzymes Myocardial infarction Creatinine Chronic renal failure Fasting blood sugar Diabetes mellitus Haemoglobin Iron deficiency anaemia Liver function test Hepatoma Lumbar puncture Meningitis Papanicolaou smear Ca-in-situ of cervix Prothrombin index Haemophilia Serology AIDS