A medical laboratory or clinical laboratory is a laboratory where tests are done on clinical specimens in order to get information about the health of a patient as pertaining to the diagnosis, treatment, and prevention of disease.
Laboratory medicine is generally divided into two sections, each of which being subdivided into multiple units. These two sections are
- Anatomic pathology: units included here are histopathology, cytopathology, and electron microscopy. Academically, each unit is studied alone in one course. Other courses pertaining to this section include anatomy, physiology, histology, pathology, and pathophysiology.
- Clinical pathology, which includes:
- Clinical Microbiology: This encompasses five different sciences (units). These include bacteriology, virology, parasitology, immunology, and mycology.
- Clinical Chemistry: Units under this busy section include instrumental analysis of blood components, enzymology, toxicology and endocrinology.
- Hematology: This section consists of automated and manual analysis of blood cells. It includes two subunits, which are coagulation and blood bank.
- Genetics is also studied along with a subspecialty known as cytogenetics.
- Reproductive biology: Semen analysis, Sperm bank and assisted reproductive technology.
Distribution of clinical laboratories in health institutions varies greatly from one place to another. For instance, for microbiology, some health facilities have a single laboratory for microbiology, while others have a separate lab for each unit, with nothing called a "microbiology" lab.
The following is a detailed breakdown of the responsibilities of each unit:
- Microbiology receives almost any clinical specimen, including swabs, feces, urine, blood, sputum, cerebrospinal fluid, synovial fluid, as well as possible infected tissue. The work here is mainly concerned with cultures, to look for suspected pathogens which, if found, are further identified based on biochemical tests. Also, sensitivity testing is carried out to determine whether the pathogen is sensitive or resistant to a suggested medicine. Results are reported with the identified organism(s) and the type and amount of drug(s) that should be prescribed for the patient.
- Parasitology is a microbiology unit that investigates parasites. The most frequently encountered specimen here is faeces. However, blood, urine, sputum, and other samples may also contain parasites.
- Virology is concerned with identification of viruses in specimens such as blood, urine, and cerebrospinal fluid.
- Hematology works with whole blood to do full blood counts, and blood films as well as many other specialised tests.
- Coagulation requires citrated blood samples to analyze blood clotting times and coagulation factors.
- Clinical Biochemistry usually receives serum or plasma. They test the serum for chemicals present in blood. These include a wide array of substances, such as lipids, blood sugar, enzymes, and hormones.
- Toxicology mainly tests for pharmaceutical and recreational drugs. Urine and blood samples are submitted to this lab.
- Immunology/Serology uses the concept of antigen-antibody interaction as a diagnostic tool. Compatibility of transplanted organs is also determined.
- Immunohaematology, or Blood bank determines blood groups, and performs compatibility testing on donor blood and recipients. It also prepares blood components, derivatives, and products for transfusion. Regulated by the FDA since giving blood is considered a drug, this unit determines a patient's blood type and Rh status, checks for antibodies to common antigens found on red blood cells, and cross matches units that are negative for the antigen.
- Urinalysis tests urine for many analytes. Some health care providers have a urinalysis laboratory, while others don't. Instead, each component of the urinalysis is performed at the corresponding unit. If measuring urine chemicals is required, the specimen is processed in the clinical biochemistry lab, but if cell studies are indicated, the specimen should be submitted to the cytopathology lab, and so on.
- Histopathology processes solid tissue removed from the body (biopsies) for evaluation at the microscopic level.
- Cytopathology examines smears of cells from all over the body (such as from the cervix) for evidence of inflammation, cancer, and other conditions.
- Electron microscopy prepares specimens and takes micrographs of very fine details by means of TEM and SEM.
- Genetics mainly performs DNA analysis.
- 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).
- Surgical pathology examines organs, limbs, tumors, fetuses, and other tissues biopsied in surgery such as breast mastectomys.
Medical laboratory staff
The staff of clinical laboratories may include:
- Clinical Biochemist
- Pathologists' Assistant (PA)
- Biomedical Scientist (BMS) in the UK, Medical Laboratory Scientist (MT, MLS or CLS) in the US or Medical Laboratory Technologist in Canada
- Medical Laboratory Technician (MLT in US)
- Medical Laboratory Assistant (MLA)
- Phlebotomist (PBT)
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 patients. Private (or community) laboratories receive samples from general practitioners, insurance companies, clinical research sites and other health clinics for analysis. These can also be called reference laboratories where more unusual and obscure tests are performed. For extremely specialised tests, samples may go to a research laboratory. A lot of samples are sent between different labs for uncommon tests. It is more cost effective if a particular laboratory specializes in a rare test, receiving specimens (and money) from other labs, while sending away tests it cannot do.
In many countries there are mainly three types of Medical Laboratories as per the types of investigations carried out. 1. Clinical Pathology 2. Clinical Microbiology & 3. Clinical Biochemistry laboratories. 1. Clinical Pathology: Haematology, Histopathology, Cytology, Routine Pathology2. Clinical Microbiology: Bacteriology, Mycobacteriology, Virology, Mycology, Parasitology, Immunology, Serology.3. Clinical Biochemistry: Biochemical analysis, Hormonal assays etc.Blood Banks:- Blood bank is a separate body. Its laboratory need Microbiological analysis for infectious diseases that may be found in blood. Pathology to observe Blood grouping, Haematology & cross matching reactions. It also involves PRO department for the communication & contact for blood donations etc.. Molecular diagnostic lab or cytogenetics and molecular biology lab is the latest addition to the three types of medical laboratories listed above in many countries.
Specimen processing and work flow
Sample processing 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 the 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. This label has a barcode that can be scanned by automated analyzers and test requests uploaded from the LIS. Entry of requests onto a laboratory management system involves typing, or scanning (where barcodes are used) in the laboratory number, and entering the patient identification, as well as any tests requested. This allows laboratory machines, computers and staff to know what tests are pending, and also gives a place (such as a hospital department, doctor or other customer) for results to go.
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.
Many specimens end up in one or more sophisticated automated analysers, that process a fraction of the sample and return one or more "results". Some laboratories use robotic sample handlers (Laboratory automation) to optimize the workflow and reduce contamination risk and sample handling of the staff.
The work flow in a lab is usually heavy from 2:00 am to 10:00 am. Nurses and doctors generally have their patients tested at least once a day with general complete blood counts and chemistry profiles. These orders are then drawn during a morning run by phlebotomists for results to be available in the patient's charts for the attending physicians to consult during their morning rounds. Another busy time for the lab is after 3:00 pm when private practice physician offices are closing. Couriers will pick up specimens that have been drawn throughout the day and deliver them to the lab. Also, couriers will stop at outpatient drawing centers and pick up specimens. These specimens will be processed in the evening and overnight to ensure results will be available the following day.
Laboratories today are held together by a system of software programs and computers that exchange data about patients, test requests, and test results known as a Laboratory information system or LIS. The LIS is interfaced with the hospital information system.
This system enables hospitals and labs to order the correct test requests for each patient, keep track of individual patient or specimen histories, and help guarantee a better quality of results as well as printing hard copies of the results for patient charts and doctors to check.
Result analysis, validation and interpretation
According to ISO 15189 norm, all pathological results must be verified by a competent professional. In some countries staff like clinical scientists do the majority of this work inside the laboratory with abnormal results referred to the relevant pathologist. In others, only medical staff (pathologist or clinical biologist) is concerned by this phase. It can be assisted by some software in order to validate normal or non modified results. Medical staff are sometimes also required in order to explain pathology results to physicians. For a simple result given by phone or for a technical problem it's a medical technologist or medical lab scientist explaining it to a registered nurse.
Departments in some countries are exclusively directed by a specialized pathologist, in others a consultant, medical or non-medical, may be the Head of Department. Clinical scientists have the right to interpret and discuss pathology results in their discipline in many countries, in Europe they are qualified to at least Masters level, may have a PhD and can have an exit qualification equivalent to medical staff (e.g., FRCPath in the UK). In France, only medical staff (Pharm.D. and M.D. specialized in anatomical pathology or clinical biology) can discuss pathological results, clinical scientists are not considered as a part of medical staff.
Medical laboratory accreditation
Credibility of medical laboratories is paramount to the health and safety of the patients relying on the testing services provided by these labs. The international standard in use today for the accreditation of medical laboratories is ISO 15189 - Medical laboratories - particular requirements for quality and competence.
Accreditation is done by the Joint Commission, College of American Pathologists, AAB (American Association of Bioanalysts), and other state and federal agencies. CLIA 88 or the Clinical Laboratory Improvement Amendments also dictate testing and personnel.
The accrediting body in Australia is NATA, all laboratories must be NATA accredited to receive payment from Medicare.
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- Farr, J. Michael; Laurence Shatkin (2004). Best jobs for the 21st century. JIST Works. p. 460. ISBN 1-56370-961-9.
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