In medicine, sampling is gathering of matter from the body to aid in the process of a medical diagnosis and/or evaluation of an indication for treatment, further medical tests or other procedures. In this sense, the sample is the gathered matter, and the sampling tool or sampler is the person or material to collect the sample.

Sampling is a prerequisite for many medical tests, but generally not for medical history, physical examination and radiologic tests.

By sampling technique[link]

• A biopsy is the removal of tissues from the body, generally in the sense of solid or soft tissue targets. Examples of biopsy procedures are bone marrow biopsy, brain biopsy, skin biopsy and liver biopsy.
• Cytopathologic sampling particularly involves gathering of cells to detect abnormalities, generally not preserving the normal tissue structure. Puncture (also called centesis) followed by aspiration is the main method used for cytopathologic sampling. Examples are thoracocentesis to sample pleural fluid, and amniocentesis to sample amniotic fluid. The main method of centesis, in turn, is fine needle aspiration, but there are also somewhat differently designed needles, such as for bone marrow aspiration. Another method of cytopathologic sampling is a Pap test, in which cells are scraped off with a spatula that is inserted transvaginally without having to puncture any tissue.

By sampled matter[link]

Different types of matter that are sampled can be categorized by solidness versus fluidity, such as:

• Solid material, such as in bone marrow biopsy
• Soft material, such as in a muscle biopsy
• Body fluids

Body fluid sampling[link]

Body fluid sampling include:

• Blood sampling for any blood test, including:
  • Arterial blood sampling, such as by radial artery puncture
  • Capillary blood sampling, generally by using a blood lancet for puncture, followed by sampling by capillary action with a test strip or small pipe
  • Venous blood sampling, also called venipuncture
• Cerebrospinal fluid sampling, generally by lumbar puncture
• Pleural fluid sampling, generally by thoracocentesis
• Amniotic fluid sampling, generally by amniocentesis
• Sampling of fluid of the peritoneal cavity, generally by peritoneocentesis (also called laparocentesis). It can be used for cytology to detect spread of gynecologic cancers.

By component of interest[link]

The sampled matter can be analyzed for various components, for example:

• Electrolytes
• Proteins
• cells, such as white blood cells in blood sampling
• Microbiological agents, such as bacteria or fungi

Microbiological sampling[link]

Microbiological sampling include:

• Blood sampling for blood cultures, performed similarly as that for tests on the fluid itself above
• Throat swab for throat culture. It's performed by applying a cotton swab to the surface of the throat.
• Sampling of sputum from the lungs for sputum culture. It can be performed by special techniques of coughing, or by a protected specimen brush (PSB),^[1] which is a brush that can be retracted into a plastic tube to prevent contamination of bacteria in the throat while inserting and removing the instrument.

References[link]