The Disciplines of Pathology

At the present time, pathology has nine major areas of activity. These relate either to the methods used or the types of disease which they investigate. The disciplines are:

Anatomical Pathology
deals with the tissue diagnosis of disease, usually from biopsy materials taken from a patient in the operating theatre or on a ward, or from an autopsy (post mortem).
Sub specialities include:
  • histology – the preparation of samples of body tissue for tests to diagnose and detect disease.
  • cytology – the performing of tests on samples of body cells to detect cancer,
  • forensic pathology – the analysis of criminal cases and assisting the police in their investigations,
Example test: PAP smear for cervical cancer.
Chemical Pathology or Biochemistry
deals with the entire spectrum of illness, often involving detecting changes in a wide range of substances in blood and body fluids (electrolytes, enzymes and proteins) that change in many diseases. In addition, it involves detecting and measuring tumour (cancer) markers, hormones, vitamins, poisons and both therapeutic and illicit drugs.
Example test: cholesterol and triglycerides to diagnose risk factors for heart disease.
Clinical Pathology
the subspecialty of pathology that is familiar with the major aspects of the clinical branches of laboratory medicine. He or she is usually trained in chemical pathology, microbiology, haematology and blood banking, though not in as much detail as subspecialists in each field. Their role is similar to a General Pathologists but unlike General Pathologists they do not do Anatomical Pathology. A clinical pathologist would usually work in a medium sized private practice, community hospital or a large country town or other non-metropolitan centre. For problems demanding specific expertise they would consult with more specialised colleagues. Some, however, also work as part of the team in large metropolitan public or private practices particularly in managing common high volume tests from more than one discipline.
Forensic Pathology
the subspecialty of Pathology that focuses on medicolegal investigations of sudden or unexpected death.

A Forensic Pathologist is primarily involved identifying the cause of death and reconstructing the circumstances by which the death occurred. This is performed in a meticulous, painstaking manner. A major component of the role involves the performance of autopsy examinations to both the external and internal body organs to discover cause of death. They also look at tissue sample from bodies under the microscope to assist in establishing the underlying pathological basis for the cause of death.
Forensic Pathologists are occasionally required to visit crime scenes or accidents or to testify in court.

Genetics
includes three main branches –cytogenetics (microscopic analysis of chromosomal abnormalities), molecular genetics (uses DNA technology to analyse mutations in genes) and biochemical genetics (specialized biochemical testing to identify specific markers). It involves tests on chromosomes, DNA and specific biochemical markers from body fluids, cells in body fluids and tissues to diagnose genetic diseases.

Example tests: Cystic fibrosis (gene test), Down syndrome (chromosomal test), maple syrup urine disease (biochemical genetic test)

Haematology
deals with many aspects of diseases which affect the blood, such as anaemia, leukaemia, lymphoma and clotting or bleeding disorders. It also encompasses the subspecialty of transfusion medicine, which includes blood typing and compatibility testing and the management and supply of a large range of blood products.
Example test: INR (clotting test) to check warfarin dosage is correct.
Immunology
Immune function tests can determine whether an individual is allergic, and if so, to what. Many diseases result from the immune system defense systems inappropriately targeting normal organs systems resulting in “auto-immune diseases”. For this reason, many other immunological tests constitute diagnostic markers for disorders such as lupus, rheumatoid arthritis, diabetes and thyroid conditions. Other immunological tests monitor tissue injury due to inflammation.
Example test: SLE (lupus).
Microbiology
deals with diseases caused by infectious agents such as bacteria, viruses, fungi and parasites through tests on blood, body fluids and tissue samples. Additional areas involve control of outbreaks of infectious disease and dealing with the problems of infections caused by antibiotic-resistant bacteria.
Example test: urine sample to detect urinary tract infection.
General Pathology
covers all areas of pathology at less specialised levels.
Example test: Pathology laboratories have general pathologists managing tests from more than one discipline, including: chemical and anatomical pathology, haematology and microbiology.