In
medicine
Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pr ...
, sampling is gathering of
matter
In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic part ...
from the body to aid in the process of a
medical diagnosis
Medical diagnosis (abbreviated Dx, Dx, or Ds) is the process of determining which disease or condition explains a person's symptoms and signs. It is most often referred to as diagnosis with the medical context being implicit. The information r ...
and/or evaluation of an
indication for treatment, further
medical test
A medical test is a medical procedure performed to detect, diagnose, or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging, genetic ...
s 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 test
A medical test is a medical procedure performed to detect, diagnose, or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging, genetic ...
s, but generally not for
medical history
The medical history, case history, or anamnesis (from Greek: ἀνά, ''aná'', "open", and μνήσις, ''mnesis'', "memory") of a patient is information gained by a physician by asking specific questions, either to the patient or to other peo ...
,
physical examination
In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally consists of a series of questions about the pati ...
and
radiologic test
Radiology ( ) is the medical discipline that uses medical imaging to diagnose diseases and guide their treatment, within the bodies of humans and other animals. It began with radiography (which is why its name has a root referring to radiatio ...
s.
By sampling technique
*Obtaining excretions or materials that leave the body anyway, such as
urine
Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra.
Cellul ...
,
stool,
sputum, or
vomitus
Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose.
Vomiting can be the result of ailments like food poisoning, gastroenterit ...
, by direct collection as they exit. A sample of
saliva
Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can ...
can also be collected from the mouth.
Excision (cutting out), a surgical method for the removal of solid or soft tissue samples.
*Puncture (also called ''centesis'') followed by aspiration is the main method used for sampling of many types of tissues and body fluids. Examples are
thoracocentesis to sample
pleural fluid, and
amniocentesis to sample
amniotic fluid
The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products between ...
. 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. Puncture ''without'' aspiration may suffice in, for example,
capillary blood sampling.
* Scraping or swiping. In a
Pap test, cells are scraped off a
uterine cervix with a special
spatula and brush or a special broom device that is inserted through a vagina without having to puncture any tissue.
Epithelial cell
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
s for
DNA testing can be obtained by swiping the inside of a cheek in a mouth with a swab.
Biopsy or cytopathology
In terms of sampling technique, a
biopsy
A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a dise ...
generally refers to a preparation where the normal tissue structure is preserved, availing for examination of both individual cells and their organization for the study of
histology
Histology,
also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures v ...
, while a sample for
cytopathology is prepared primarily for the examination of individual cells, not necessarily preserving the tissue structure. Examples of biopsy procedures are
bone marrow biopsy,
brain biopsy,
skin biopsy and
liver biopsy.
By sampled matter
Different types of matter that are sampled can be categorized by solidness versus fluidity, such as:
*Solid tissue, such as in
bone marrow biopsy
*Soft tissue, such as in a
muscle biopsy
In medicine, a muscle biopsy is a procedure in which a piece of muscle tissue is removed from an organism and examined microscopically. A muscle biopsy can lead to the discovery of problems with the nervous system, connective tissue, vascula ...
*
Body fluid
Body fluids, bodily fluids, or biofluids, sometimes body liquids, are liquids within the human body. In lean healthy adult men, the total body water is about 60% (60–67%) of the total body weight; it is usually slightly lower in women (52-55%). ...
s such as
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
Body fluid sampling
Body fluid sampling includes:
*
Blood sampling for any
blood test, including:
**
Arterial blood sampling, such as by
radial artery puncture
Radial artery puncture is a medical procedure performed to obtain a sample of arterial blood for gas analysis. A needle is inserted into the radial artery and spontaneously fills with blood. The syringe is either prepacked with a small amount of ...
. This can be done for
arterial blood gas analysis.
**
Capillary blood sampling, generally by using a
blood lancet for puncture, followed by sampling by
capillary action with a test strip or small pipe. This is common for routine
diabetic
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level (hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
monitoring for
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
.
**
Venous blood sampling, also called ''phlebotomy''. It is generally done by
venipuncture (which can also be used for
intravenous therapy). Other than routine diabetic monitoring for glucose, the majority of
blood tests are done on samples of venous blood taken by a
health professional
A health professional, healthcare professional, or healthcare worker (sometimes abbreviated HCW) is a provider of health care treatment and advice based on formal training and experience. The field includes those who work as a nurse, physician (suc ...
, including
phlebotomists who are specifically trained in venipuncture. Such samples are commonly collected in capped
test tubes, often with a small amount of some sort of preservative.
*
Cerebrospinal fluid
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.
CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...
sampling, generally by
lumbar puncture
*
Pleural fluid sampling, generally by
thoracocentesis
*
Amniotic fluid
The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products between ...
sampling, generally by
amniocentesis
*
Peritoneal fluid
Peritoneal fluid is a serous fluid made by the peritoneum in the abdominal cavity which lubricates the surface of tissue that lines the abdominal wall and pelvic cavity. It covers most of the organs in the abdomen. An increased volume of peritone ...
sampling, generally by
peritoneocentesis (also called ''laparocentesis''). It can be used for
cytology to detect spread of
gynecologic cancers.
By component of interest
The sampled matter can be analyzed for various components, for example:
*
Electrolytes
*
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
s
*
cells
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
, such as
white blood cells in blood sampling
*Microbiological agents, such as bacteria or fungi
Microbiological sampling
''
Microbiological sampling'' include:
*''Blood sampling'' for
blood culture
A blood culture is a medical laboratory test used to detect bacteria or fungi in a person's blood. Under normal conditions, the blood does not contain microorganisms: their presence can indicate a bloodstream infection such as bacteremia ...
s, performed similarly as that for tests on the fluid itself above
*''Throat swab'' for
throat culture. It is performed by applying a
cotton swab to the surface of the
throat.
*Sampling of
sputum from the
lungs
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either si ...
for
sputum culture. It can be performed by special techniques of coughing, or by a ''protected specimen brush'' (PSB),
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
{{reflist
Biological techniques and tools
Biological specimens