A medical laboratory or clinical laboratory is a laboratory where tests are done on biological specimens in order to get information about the health of a patient.

Departments

The laboratory is often divided into a number of disciplines:

• Microbiology receive swabs, faeces, urine, blood, sputum, medical equipment, as well as possible infected tissue. They culture this to check for any abnormal bacteria.

• Haematology receive whole blood and citrated plasma. They do full blood counts, blood films and coagulation investigations.

• Biochemistry usually receive serum. They test the serum for different components.

• Immunology test for antibodies against the bodies own cells.

• Serology receive serum samples to look for evidence of diseases such as hepatitis or HIV.

• Histology process solid tissue removed from the body to make slides and examine cellular detail.

• Cytology examine smears of cells (such as from the cervix) for evidence of cancer and other conditions.

• Cytogenetics involves using blood and other cells to get a karyotype. This can be helpful in prenatal diagnosis (e.g. Down's syndrome) as well as in cancer (some cancers have abnormal chromosomes).

• Virology and DNA analysis are also done in large medical laboratories.

Types of laboratory

In many countries, there are two main types of labs that process the majority of medical specimens. Hospital laboratories are attached to a hospital, and perform tests on these patients. Private (or community) laboratories receive samples from general practitioners, insurance companies, and other health clinics for analysis.

For extremely specialised tests, samples may go to an environmental science or research laboratory.

A lot of samples are sent between different labs for uncommon tests. It is more cost effective if a particular laboratory specialises in a rare test, receiving specimens (and money) from other labs, while sending away tests it cannot do.

Sample processing

What happens to a sample after it has been taken varies between localities and labs, but it will usually start with a set of samples and a request form.

Typically a set of vacutainer tubes containing blood, or any other specimen will arrive to a laboratory in a small plastic bag, along with the form.

The form and the specimens are given a laboratory number. The specimens will usually all receive the same number, often as a sticker that can be placed on the tubes and form. Sometimes different departments use different numbering systems. For instance if microbiology uses a different system to biochemistry, the microbiology samples are given one number, the chemistry samples another. When this occurs, the form often gets two numbers and is entered twice.

Data entry involves typing in the form number, and entering the patient identification, as well as any tests requested. This allows laboratory machines and computers to know what tests are pending, and also gives a place for results to go.

What happens to the specimens after they are numbered depends on the department. For biochemistry samples, blood is usually centrifuged and serum is separated. If the serum needs to go on more than one machine, it can be divided into separate tubes.

See also

• medicine