What is pathology?

Image of blood tubes

Pathology is a medical specialty looking at disease processes and their cause. Body tissue, blood and other bodily fluids are analysed to assist medical practitioners in identifying the cause and severity of disease, and to monitor treatment.

Pathologists

Pathologists are specialist doctors who work in this field. They oversee laboratory testing, much of which is performed by scientific and technical staff. Pathologists are often involved in research, education and clinical consultation, and also play an important role in result interpretation.

Pathology is made up of these specialty areas:

Anatomical Pathology

Anatomical Pathology is the microscopic study of organs and tissues to determine the causes and effects of particular diseases. Specialist pathologists, Anatomical Pathologists, examine tissue to aid in the diagnosis of disease and the determination of a treatment plan. Specimens that can be examined include:

  • Solid tissue from living persons: a tissue specimen can be obtained from almost any organ or any part of the body by using various biopsy techniques.
  • Solid tissue from an autopsy (post-mortem). This may be undertaken to establish the cause of sudden or unexpected death, to examine disease progression or in the investigation of criminal cases (forensic pathology) to assist the police.
  • Specimens of separated cells in fluids or tissue smears (Cytology), often for the diagnosis and prevention of cancer. Examples of cytological assessment are Pap smears for cervical cancer screening and fine needle aspiration of a palpable lesion (eg. breast lumps) to check for malignancy.

ACT Pathology provides comprehensive quality diagnostic pathology services in tissue pathology and cytopathology.

Preparation of tissue for examination is a complex process that is supported by scientific and technical staff. Registrars are trained to select sections of the tissue samples for processing and these are embedded in wax and further sectioned into slides. Routine and special stains are used to aid the pathologists in their examination of these slides under high-powered microscopes.

ACT Pathology is one of a limited number of pathology laboratories in Australia to have an Electron Microscopy Unit. The electron microscope can magnify very small details using electrons rather than light, magnifying at levels up to 300,000 times for biological specimens. Specimens that are examined using the electron microscope include kidney tissue and tumour biopsies.

Chemical Pathology

Chemical Pathology is the study of chemical and biochemical mechanisms of the body in relation to disease. A chemical pathology department within a hospital provides a link between medicine and the basic sciences employing analytical and interpretative skills to aid the clinician in the prevention, diagnosis and treatment of disease.

The biochemistry department monitors treatment such as diabetics, patients on lipid lowering drugs, fluid balance, thyroid disease and therapeutic drug levels. It also provides a screening service such as neonatal screening for cystic fibrosis and screening for drugs of abuse.

In many diseases there are significant changes in the chemical composition of body fluids. Testing is aimed at detecting these changes quantitatively compared to results from healthy people. Some typical examples are:

  • a raised blood sugar in diabetes mellitus due to lack of insulin;
  • raised blood enzymes due to their release from heart muscles after heart attack;
  • raised blood excretion products in kidney disease; and
  • lowered blood sex hormones in an infertile female with ovarian failure.

These changes can be used for the diagnosis of disease and also monitoring treatment. For example:

  • to monitor diabetic control in known diabetics for effective treatment, and
  • to assess kidney function after transplantation by the measurement of imuunosupressive drug levels.

Blood is a complex body fluid with hundreds of different components - consequently a wide range of methods is used to measure components. The sample type for most tests is blood plasma or serum.

In our laboratory we aid in all of the above plus perform a full range of protein and tumour marker analysis, a full range of hormone analyses (Thyroid, fertility) as well as measurement of low concentration elements such as aluminium and other heavy metals. We also test for adrenal and carcinoid tumours using specialised techniques.

We also maintain a blood gas point of care network within the Canberra Hospital Campus to aid clinicians in the treatment of critically ill patients.

Cytogenetics

This involves the analysis of abnormalities at a chromosomal level. Techniques have been developed using high-powered microscopes which are used to look at the number and structure of chromosomes so that genetic conditions such as Downs Syndrome can be diagnosed.

ACT Pathology has a Cytogenetics laboratory that performs a range of testing including:

  • blood testing for genetic disorders relating to miscarriage or infertility, and paediatric investigations (eg. delayed development);
  • prenatal testing;
  • bone marrow testing of haematological malignancies.

Haematology

Haematology is the field of medicine involved in the study of blood. Investigations that take place in the Haematology laboratory include:

  • Routine haematology testing (FBC)
    Specimens of whole blood are analysed by a specialised instrument called a Coulter Counter which measures the number and size of blood cells such as red cells, white cells and platelets. A blood film is made by smearing a drop of blood on a microscope slide. These slides are reviewed by trained scientists and Haematologists to diagnose a number of diseases eg. anaemia or acute leukaemia. The picture on the right depicts a normal blood film.
  • Clotting and bleeding studies
    Includes testing relating to diseases that cause improper clotting or excessive bleeding. Anticoagulant monitoring is also offered.
  • Transfusion services
    Blood grouping and identification of blood group antibodies and cross-matching of blood for transfusions.
    The Haematologists provide advice and guidance in the appropriate use of blood and blood products and manage Haemophilia treatment.
  • Malaria
    Malarial films (thick and thin) and a rapid test for Falciparum malaria are performed in Haematology

Immunology

Clinical Immunology is concerned with the diagnosis and management of diseases arising from abnormal immune responses. In broad terms, these abnormalities may be the result of either under activity (immunodeficiency) or over activity (autoimmunity and allergy) of the immune system.

The diagnostic Immunology laboratory performs tests that identify, quantify and characterise immune defects. For example, the integrity of the immune system can be assessed by measurement of total serum antibodies (IgG, IgA, and IgM), circulating lymphocyte subsets, and complement studies. Measurement of autoantibodies (eg ANA, rheumatoid factor) is crucial for the diagnosis of certain autoimmune diseases. Measurement of antibodies to allergens such as dust mite can be useful in assessing patients with allergic disease.

The immune system normally functions to fight infections, and looking for antibodies to particular infections is an important way of confirming recent or remote contact with bacteria and viruses. These investigations, called serology, make up another large part of the work of the Immunoassay laboratory. For example, antibodies to HIV, Syphillis, Hepatitis C, Chlamydia, Ross River Virus, and Mycoplasma,Influenza are used to confirm past, recent, or active infection.

Immunology also studies the persons ability to identify and destroy foreign agents. It studies quantitative as well as functional assessment of lymphocytes eg proliferation assays for immunodeficiency disorders.

Microbiology

Microbiology deals with isolation and identification of infectious agents such as bacteria, viruses, fungi and parasites that cause disease.

The microbiologist cultures organisms from specimens such as urines, faeces and swabs to identify pathogens (disease-causing organisms). Where bacterial pathogens are identified they can be subject to antibiotic susceptibility testing to assist clinicians to select the appropriate treatment.

The range of microbiology testing conducted at ACT Pathology includes:

  • bacteriology- the isolation and rapid identification of bacterial pathogens;
  • Antimicrobial susceptibility testing;
  • mycology- the isolation and identification of dermatophytes relating to fungal infections;
  • virology;
  • hospital infection surveillence control- the isolation and identification of antibiotic resistant pathogens such as MRSA and VREs;
  • parasitology;
  • sexual health microbiology; and
  • bacterial environment testing.

ACT Pathology participates in several Australia-wide projects looking at the extent of antibiotic resistance particularly involving Pneumococcus, Staphylococcus aureus and Haemophilus influenzae as part of the Australian Group on Antimicrobial Resistance (AGAR).

The microbiology staff also work closely with the hospital infection control teams to review wound infections, nosocomial infections and outbreaks of hospital cross-infection.

Molecular Pathology

Molecular pathology is a term commonly used to encompass all forms of diagnostic DNA and RNA tests (also referred to as nucleic acid tests). The completion of the human genome project and the sequencing of many bacterial and viral genomes has revolutionised the way we detect genetic disease and many infectious organisms. As a result nucleic acid detection techniques are replacing many conventional laboratory methods such as viral culture.

Molecular Pathology at ACT Pathology provides a range of genetic testing for the more common inherited disorders such as cystic fibrosis, hereditary haemochromatosis and fragile X. It also provides a rapidly expanding range of highly sensitive tests for the detection of pathogenic organisms such as hepatitis C, chlamydia and gonorrhoea. As well as the increased sensitivity, nucleic acid detection techniques can provide rapid results for the detection of meningococcal disease and various other life-threatening organisms.