Disciplines in laboratory pathology
Laboratories are typically divided into sections or departments according to scientific discipline. Sometimes, the labs collaborate. In leukaemia, for instance, haematology, biochemistry, molecular pathology, cytogenetics, immunology and microbiology can be all working together on behalf of a single patient.
In some large diagnostic laboratories testing from two or more disciplines may be gathered together to make best use of the available technology and the specialist skills and training of staff.
Many illnesses change the levels of chemicals in the body and this means that the biochemistry lab is often the busiest of all. It is here they perform many of the most commonly-requested tests. Among them is the E/LFT which measures electrolytes and liver function and gives a good picture of a patient’s general health. Biochemistry is also responsible for performing cholesterol, triglycerides and lipids tests, used to screen for cardiovascular disease, and blood glucose to diagnose and monitor diabetes. They will also measure metabolic products, proteins and drugs, mainly in blood but also in urine, CSF and other body fluids.
The pathologists and scientists working in haematology specialise in the blood and bone marrow (where blood cells are formed). Some further specialise in areas such cancers of the blood, where they lead multi-disciplinary teams diagnosing and managing leukaemia and lymphoma. This includes looking for abnormal cells and cell patterns under the microscope. Others specialise in coagulation (blood clotting) – important in a range of illnesses from stroke, heart disease and post-surgery treatment to pulmonary embolism and Deep Vein Thrombosis. The Full Blood Count, one of the most commonly-requested tests because it can tell so much about a patient’s health, is performed here. Blood banking (see also Blood banking, Understanding Your Tests), blood typing and antibody testing are also part of haematology’s work.
The investigation of infectious diseases is carried out in microbiology. The pathologists and scientists working here look for specific bacteria, viruses, fungi and parasites that may be causing a patient’s symptoms. The work can involve growing (or culturing) a particular bacteria in an incubator that mimics the perfect environment for the microorganism, then examining the results under the microscope (microscopy). This lab also measures the susceptibility of the bacteria to antibiotics to help decide on treatment.
Central to the body’s ability to fight infection is the production of antibodies - proteins produced in response to a foreign organism or substance. Without adequate levels of antibodies, the body’s defence is lowered but high levels of antibodies can be indicative of autoimmune disease.
Immunology specialises in disorders of the immune system including autoimmune disorders such as rheumatoid arthritis, SLE (lupus), Crohn’s disease and coeliac disease. It also performs tests to establish whether or not someone is immunodeficient. This can be inherited, the result of an infection or a disease, or produced as a side effect of drugs, such as those used to treat cancer.
In some diseases it’s not possible to identify the bacteria or virus that is causing an infection, instead, the antibodies produced by the immune response are investigated. The scientists working in serology examine blood serum for antibodies to infections such as colds and flu, Epstein Barr virus (glandular fever), rubella (measles) and Ross River fever. Allergies are also tested in this way. One of the most common tasks performed in the serology lab is to measure levels of antibodies to find out if a patient has had a recent infection, a past infection, or a response to a vaccination. In some cases, antibody tests can help monitor a patient’s treatment to see if it is being effective.
Molecular Pathology and Cytogentics
This is one of the newest areas of pathology where specialists use advanced technology to investigate genes and chromosomes. They could be looking for gene mutations and chromosomal abnormalities caused by an inherited condition, or chromosomal changes and gene mutations (somatic) created as part of the cancer process. By identifying the type of mutations or specific chromosome abnormalities, a sub classification of cancer can be diagnosed, which is important in making decisions about treatment. For more see Genetic testing, Understanding Your Tests.
This testing is performed with technologies such as fluorescent in-situ hybridization (FISH) and the Polymerase Chain Reaction (PCR). The same techniques are also used to look for the genetic evidence of bacteria or viruses, providing a quicker way of testing for infections than conventional methods.
Histopathology or tissue pathology is the microscopic investigation of tissue, obtained from the body by surgical removal or by needle biopsy of a solid core of tissue. For more on histopathology see Anatomical pathology, Understanding Your Tests
Here, pathologists and scientists look for cancerous changes in cells that are either shed in body fluids or collected by smears and scrapings. Samples being investigated include Pap smears and liquid-based cervical smears, fine needle aspirations of tumours and bodily fluids such as urine. Investigation is by microscopy and is highly dependent on the observational skills and professional judgement of the pathologist or scientist. For more on cytology see Anatomical pathology, Understanding Your Tests.