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Careers and Specialties

What do MLTs do?

Every day in laboratories across Ontario, medical laboratory technologists (MLTs) perform thousands of sophisticated medical tests on blood, body fluids and tissues.

The results of these tests provide important information – information doctors and other health professionals need to make decisions about their patients’ health. In fact, the majority of all clinical decisions are based on laboratory testing data.

MLTs are one of the largest groups of health professionals in Ontario, and are at the heart of many of the major innovations taking place in health care. Medical laboratory science is a field that offers many opportunities in variety of specialties.

Working closely with other members of the health care team, MLTs use their skills and expertise to help detect illness, monitor health and support wellness. They perform many critical roles in today’s health care organizations, working in areas including:

  • Clinical Chemistry: Measuring chemical components of blood and body fluids including hormones and drugs.
  • Clinical Microbiology: Studying bacteria, fungi, viruses, and parasites that invade the body.
  • Diagnostic Cytology: Studying cells for the detection of cancer.
  • Genetics: Studying chromosomes, DNA and RNA from cells of body fluids and tissues to diagnose genetic diseases.
  • Electron Microscopy: Preparing highly magnified photographs of cells to capture details ordinary microscopes cannot detect.
  • Hematology: Studying diseases in blood cells and the clotting mechanisms of the blood.
  • Histology/Pathology: Preparing and studying body tissue for the detection of disease.
  • Immunology: Studying the body’s defence mechanisms against disease.
  • Laboratory Information Management: Using laboratory data to improve health care outcomes.
  • Patient Relations: Using sophisticated point-of-care testing technology at the bedside with patients.
  • Transfusion Science: Determining blood types and cross-matching for transfusion.

Specialties in Medical Laboratory Science

Biochemistry (Clinical Chemistry)

Biochemistry is the study of the chemical and physiochemical processes of living organisms. MLTs perform a wide variety of biochemical analyses, including those to determine cholesterol and thyroid levels, enzyme levels for heart disease, and glucose levels for the diagnosis and management of diabetes. In fact, a typical biochemistry section of a medical laboratory can perform and interpret more than 200 chemical analyses.

Clinical Genetics (Cytogenetics & Molecular Genetics)


Cytogenetics is the study of chromosomes and the diseases associated with an abnormal number or structure of chromosomes. Chromosomes are detected using a light microscope. MLTs who work in cytogenetics treat cells with chemicals to increase the number of dividing cells. The cell is then ruptured to release the chromosomes, which are then fixed, stained and examined, first using a light microscope and then using computerized digital images. MLTs in this discipline analyze prenatal samples, cancer cells, blood and tissues for genetic diseases.

Molecular Genetics

MLTs who work in molecular genetics focus on examining DNA and RNA and looking for changes in the genes. Abnormal or changed genes are, in many cases, associated with specific conditions or diseases such as breast cancer and hemophilia. Molecular techniques can identify infectious agents (like viruses and bacteria that are difficult or slow to grow in tissue cultures), and the stages of cancer and various genetic diseases.


Cytology is the study of the origin, formation, structure, function and classification of cells. The identification of normal and cancerous cells also falls within this discipline. MLTs who work in cytotechnology are responsible for specimen preparation and staining, as well as microscopic evaluation and interpretation of patient samples. One of the roles of the MLT practising cytology is to identify cancer of the cervix through the microscopic examination of Pap smears. Cytology results are used in diagnosis, patient management, and treatment follow-up.


Hematology deals with blood, blood-forming tissues and the related cellular components. Modern-day analysis is performed primarily by automated instrumentation, with MLTs conducting the interpretation. Analysis can identify cells associated with a wide variety of blood disorders such as leukemia and anemia. Hematology also includes investigating bleeding or coagulation disorders, such as hemophilia, and monitoring test results from patients taking anticoagulants.


Histology deals with the microscopic identification of cells and tissues. This science requires an understanding of the structure and composition of cells and their organization into various organs. MLTs working in histology are responsible for preparing and staining tissues for diagnostic examination under the light microscope. MLTs practising histology also work with tissue biopsies and larger specimens from operating rooms. This work is sometimes needed urgently, so surgeons can decide how to proceed in the best interest of a patient undergoing surgery.


Microbiology is the study of the bacteria, fungi, viruses, and parasites that invade the body. The microbiology lab is often divided into the following subspecialties, with MLTs working in one area or a combination.

* Bacteriology:

The identification of the bacteria that cause disease in the human body. MLTs in this discipline also test the effectiveness of various antibiotics. The MLT specializing in bacteriology may also deal with public health (e.g., the potability of water or the quality of milk) or the fight against disease (e.g., the diagnosis of hospital-acquired infections or the diagnosis of communicable diseases).

* Mycology

The study of fungi and fungoid diseases. Ringworm and thrush are two of the more common fungoid diseases identified by technologists working in this field.

* Parasitology

The specialty that examines and identifies parasites found on or in the human body. This includes identifying some of the most common parasites such as pinworm, roundworm and tapeworm. Unlike the other specialties of microbiology, parasites are often large enough to see with the naked eye.

* Virology

The science devoted to the study of viruses and viral diseases. The prevalence of AIDS and HIV has developed a greater public awareness of the devastating impact viruses can have on everyday life. MLTs working in this field focus on the identification and management of viral diseases.


Phlebotomy is the taking of blood from a vein. This procedure is often the first step in an MLT’s work. Blood samples are used to perform many of the laboratory tests ordered by physicians and other authorized health care professionals. Phlebotomy is part of a controlled act in Ontario. Controlled acts are legally authorized to regulated health professions.

Transfusion Science (Immunohematology)

MLTs working in transfusion science study antigens and antibodies associated with blood transfusions and certain complications of pregnancy. Roles range from assessing the blood to be used in surgery for accident victims, to analyzing specialized blood products such as plasma for hemophiliacs or platelets for patients with leukemia. MLTs practising in this area must have an understanding of immunology, serology and genetics. In larger centres, MLTs practising transfusion science may perform tests associated with tissue and organ transplant.