A medical laboratory or clinical laboratory is a laboratory where tests are carried out on clinical specimens in order to obtain information about the health of a patient in order to provide diagnosis, treatment, and prevention of disease. Clinical laboratories are thus focused on applied science, mainly on a production-like basis, as opposed to research laboratories that focus on basic science on an academic basis.
Medical laboratories vary in size and complexity and so offer a variety of testing services. More comprehensive services can be found in acute-care hospitals and medical centers, where 70% of clinical decisions are based on laboratory testing. Doctors offices and clinics, as well as skilled nursing and long-term care facilites, may have laboratories that provide more basic testing services. Commercial medical laboratories operate as independent businesses and provide testing that is otherwise not provided in other settings due to low test volume or complexity.
In hospitals and other patient-care settings, laboratory medicine is provided by the Department of Pathology, and generally divided into two sections, each of which will be subdivided into multiple specialty areas. The two sections are:
- Anatomic pathology: areas 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 typically includes the following areas:
- Clinical Microbiology: This encompasses several different sciences. These include bacteriology, virology, parasitology, immunology, and mycology.
- Clinical Chemistry: This area typically includes automated analysis of blood specimens, enzymology, toxicology and endocrinology.
- Hematology: This area includes automated and manual analysis of blood cells. It also often includes coagulation.
- Blood Bank involves the testing of blood specimens in order to provide transfusion and related services.
- Genetics testing may be done, along with a subspecialty known as cytogenetics.
- Reproductive biology testing is available in some laboratories, including 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 specialty area.
The following is an example of a typical breakdown of the responsibilities of each area:
- 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 responsible for examining specimens for parasites. For example, fecal samples may be examined for evidence of intestinal parasites such as tapeworms or hookworms and others.
- Virology is concerned with identification of viruses in specimens such as blood, urine, and cerebrospinal fluid.
- Hematology examines whole blood specimens to perform full blood counts. Blood films are examined as well as many other specialized tests.
- Coagulation requires citrated blood samples to analyze blood clotting times and coagulation factors.
- Clinical Biochemistry usually performs tests on serum or plasma. These tests, mostly automated, 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 may also be 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. This area 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, including microscopically. If measuring urine chemicals is required, the specimen is processed in the clinical biochemistry lab, if specialized cell studies are indicated, the specimen may 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 is a specialized process generally only found in research or university laboratories. Micrographs of prepared specimens provide 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 cases of prenatal diagnosis (e.g. Down's syndrome) as well as in some cancers which have abnormal chromosomes.
- Surgical pathology examines organs, limbs, tumors, fetuses, and other tissues biopsied in surgery such as breast mastectomies.
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)
- Histotechnologist/Histology Technician
Types of laboratory
In most developed countries, there are two main types of lab processing the majority of medical specimens. Hospital laboratories are attached to a hospital, and perform tests on their patients. Private (or community) laboratories receive samples from general practitioners, insurance companies, clinical research sites and other health clinics for analysis. For extremely specialised tests, samples may go to a research laboratory. Some tests involve specimens sent between different labs for uncommon tests. For example, in some cases it may be more cost effective if a particular laboratory specializes in a less common tests, receiving specimens (and payment) from other labs, while sending other specimens to other labs for those tests they do not perform.
In many countries there are specialized types of Medical Laboratories according to the types of investigations carried out. Organisations that provide blood products for transfusion to hospitals, such as The Red Cross, will provide access to their reference laboratory for their customers. Some laboratories specialize in Molecular diagnostic and cytogenetic testing, in order to provide information regarding diagnosis and treatment of genetic or cancer-related disorders.
Specimen processing and work flow
In a hospital setting, sample processing will usually start with a set of samples arriving with a test request, either on a form or electronically via the laboratory information system (LIS). Inpatient specimens will already be labeled with patient and testing information provided by the LIS. Entry of test requests onto the LIS 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 analyzers, computers and staff to recognize what tests are pending, and also gives a location (such as a hospital department, doctor or other customer) for results reporting.
Once the specimens are assigned a laboratory number by the LIS, a sticker is typically printed that can be placed on the tubes or specimen containers. This label has a barcode that can be scanned by automated analyzers and test requests uploaded to the analyzer from the LIS.
Specimens are prepared for analysis in various ways. For example, chemistry samples are usually centrifuged and the serum or plasma is separated and tested. If the specimen needs to go on more than one analyzer, 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 to return one or more test results. Some laboratories use robotic sample handlers (Laboratory automation) to optimize the workflow and reduce the risk of contamination from sample handling by the staff.
The work flow in a hospital laboratory is usually heaviest from 2:00 am to 10:00 am. Nurses and doctors generally have their patients tested at least once a day with common tests such as complete blood counts and chemistry profiles. These orders are typically 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.
The large amount if information processed in laboratories is managed by a system of software programs, computers, and terminology standards that exchange data about patients, test requests, and test results known as a Laboratory information system or LIS. The LIS is often interfaced with the hospital information system, EHR and/or Laboratory instruments. Formats for terminologies for test processing and reporting are being standardized with systems such as Logical Observation Identifiers Names and Codes (LOINC) and Nomenclature for Properties and Units terminology (NPU terminology).
These systems enable hospitals and labs to order the correct test requests for each patient, keep track of individual patient and specimen histories, and help guarantee a better quality of results. Results are made available to care providers electronically or by printed hard copies for patient charts.
Result analysis, validation and interpretation
According to various regulations, such as the international ISO 15189 norm, all pathological laboratory results must be verified by a competent professional. In some countries, staffs composed of clinical scientists do the majority of this work inside the laboratory with certain abnormal results referred to the relevant pathologist. Clinical scientists have the responsibility for limited interpretation of testing results in their discipline in many countries. Interpretation of results can be assisted by some software in order to validate normal or non modified results.
In other testing areas, only professional medical staff (pathologist or clinical biologist) is involved with interpretation and consulting. Medical staff are sometimes also required in order to explain pathology results to physicians. For a simple result given by phone or to explain a technical problem, often a medical technologist or medical lab scientist can provide additional information.
Medical Laboratory Departments in some countries are exclusively directed by a specialized pathologist. In others, a consultant, medical or non-medical, may be the head the department. In Europe and some other countries, Clinical Scientists with a Masters level education may be qualified to head the department. Others may have a PhD and can have an exit qualification equivalent to medical staff (e.g., FRCPath in the UK).
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. Credentialing agencies vary by country. The international standard in use today for the accreditation of medical laboratories is ISO 15189 - Medical laboratories - Requirements for quality and competence.
In the United States, accreditation is performed by the Joint Commission, College of American Pathologists, AAB (American Association of Bioanalysts), and other state and federal agencies. Legislative guidelines are provided under CLIA 88 (Clinical Laboratory Improvement Amendments) which regulates Medical Laboratory testing and personnel.
The accrediting body in Australia is NATA, where all laboratories must be NATA accredited to receive payment from Medicare.
In France the accrediting body is COFRAC (COFRAC). In 2010, modification of legislation established ISO 15189 accreditation as an obligation for all clinical laboratories.
In the United Arab Emirates, the Dubai Accreditation Department (DAC) is the accreditation body that is internationally recognised by the International Laboratory Accreditation Cooperation (ILAC) for many facilties and groups, including Medical Laboratories, Testing and Calibration Laboratories, and Inspection Bodies.
In Hong Kong, the accrediting body is Hong Kong Accreditation Service (HKAS). On 16 February 2004, HKAS launched it's medical testing accreditation programme.
In Canada, laboratory accreditation is not mandatory, but is becoming more and more popular. Accreditation Canada (AC) is the national reference. Different provincial oversight bodies mandate laboratories in EQA participations like LSPQ (Quebec), IQMH (Ontario) for example.
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