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Clinical Pathology Overview

What is clinical pathology?

Clinical pathology covers a wide range of laboratory functions and is concerned with the diagnosis, treatment, and prevention of disease. Clinical pathologists are doctors with special training who often direct all of the special divisions of the laboratory, which may include the blood bank, clinical chemistry and biology, toxicology, hematology, immunology and serology, and microbiology. Clinical pathology also involves maintenance of information systems, research, and quality control.

What does a clinical pathologist do?

A clinical pathologist looks at blood, urine, and other body fluid specimens under a microscope, or with other diagnostic tools, to observe levels of certain chemicals and/or other substances in the body. A diagnosis or determination to conduct further study is then made based on the test results. Specimens for examination can include any of the following:

Types of specimens used in clinical pathology

Blood

Blood is used in many tests. Blood can either be examined as a "whole," as plasma (the fluid left when red and white blood cells are removed), or as serum (a clear fluid that separates from blood when it clots).

Blood is usually drawn with a needle from a vein, usually in the forearm. (This is also called venipuncture). Sometimes, the tip of the finger is pricked and then squeezed to draw blood (called a finger stick).

Urine

Urine is also used for a wide range of tests. Urine specimens can be obtained by:

  • Random method. The patient urinates in a cup.

  • Clean catch specimen. The outer genital area has been cleaned before urinating in a cup.

  • Sterile urine test. This requires catheterization (a tube is put into the urethra and goes to the bladder to obtain urine).

Sometimes, a doctor will require the patient to do a timed test to measure substances excreted into the urine over several hours.

Sputum (also called phlegm)

Sputum can be coughed into a clean container.

Feces

Feces or stool is usually collected by the patient in a clean cardboard or plastic container.

Other body fluids

Other body fluids collected for testing may include the following:

  • Spinal fluid

  • Pleural fluids. These fluids are around the lungs and/or in the pleural cavity (the space between the two membranes that surround the lungs). 

  • Abdominal (belly) fluids

  • Joint fluids

  • Bone marrow

Other branches of pathology include:

  • Anatomic pathology. The study of tissues, organs, and tumors.

  • Cytopathology. The study of cellular changes and everything related to cells.

  • Forensic pathology. Performance of autopsies and legal pathology tests.

  • Molecular pathology. The study of DNA and RNA sequencing, genes, and genetics.

All branches of pathology can perform each area of pathology. Some pathologists specialize in these different areas. All branches may also encompass teaching and research.