Collection OF Biological Samples PDF

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Collection OF Biological Samples...

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COLLECTION OF BIOLOGICAL SAMPLES A human biological sample can be defined as any material of human origin collected with the purpose of obtaining results that collaborate in the clinical diagnosis, in the follow-up of the evolution of some pathologies and in the establishment and control of the appropriate treatment. - Sample example is: urine, feces, blood, etc. The sample must be representative (that reproduces the characteristics of the fluid, tissue and / or origin), and homogeneous (that a fraction of it contains all the components to be analyzed equally distributed). Before collecting a specimen, a careful selection must be made to ensure that the "source site" represents the site of active disease. As important as obtaining it is the handling of the sample, so there are strict rules for the correct collection, handling, transport and conservation of the sample, as well as for its proper processing in the laboratory. For a correct result in the study carried out on biological samples, it is necessary to avoid errors that can occur throughout all phases (the pre-analytical, analytical and post-analytical phase). All personnel must be aware of the importance of their activities, to contribute to the quality objectives. Biosafety precautions The inappropriate handling of a biological sample is a source of biological risk for the people who are in contact with it, even for the environment. Therefore, it is essential to use the necessary personal protection elements, depending on the type of sample and its infectious potential, to minimize the risk of biological exposure to it. - Eye protection: goggles or mask with a visor. - Face mask. - Gloves. - Coat. - Containers for specimens, leak proof and easy to seal. Comply with the recommendations for handling sharps: ● Do not rewrap needles. ● Properly arrange and use the sharps container. ● Do not transport syringes with needles. It is recommended to transfer the aspirate to a sterile tube. In the event of an accident with biological risk, notify immediately according to the recommendations of the protocol of work accident with institutional biological risk.

Types of samples and collection

The biological samples that are most used in the laboratory for diagnostic purposes are: Blood: In clinical practice, blood is the most requested biological sample for analysis due to the large amount of information it offers on various pathologies. It is studied in various methods and with different objectives. - Capillary blood - Venous blood - Arterial blood Collection is carried out by healthcare personnel. Its derivatives plasma and serum are also used, especially the latter. ● Urine can be obtained by the patient himself in a suitable container, or obtained bypersonnel healthin case the patient is admitted, probed or when there is some kind of problem for collection. ● Stools: they can be obtained by the patient himself using a suitable container or by health personnel in the case of patients who are hospitalized. ● Semen: obtained by the patient himself in suitable conditions and container. ● Exudates: naso-pharyngeal, conjunctival, otic, vaginal, urethral. Obtaining is normally carried out by healthcare personnel, using swabs or seeding loops or probes that are put in contact with the corresponding area. ● Sputum: they are collected by the patient in a sterile container and usually those from the first expectoration in the morning. Although there are other procedures. ● Biological fluids: peritoneal, ascitic, pleural, pericardial, cerebrospinal, synovial. They are samples obtained by healthcare personnel in an invasive way because they need a puncture in the opportune cavity: abdominal, pleural, spinal canal in the spinal cord, joints, among others. ● Urinary calculus: either extracted by surgery or collected by the patient after expulsion in the urine. ● Cervical mucus: it is collected as an exudate by healthcare personnel. ● Bone marrow: by puncture and for the study of blood cells. ● Saliva: collected by the patient himself. ● Sweat: for the study of electrolytes in certain pathologies. Handling of the sample to the laboratory Both criteria will be conditioned by the type of sample and the analyzes to which it is to be submitted. Each sample must arrive in optimal conditions, perfectly labeled and accompanied by the necessary documentation to carry out the study. This information contains data on: - The patient. Both personal and clinical. - The sample. Type of sample, method of conservation, time elapsed since the sample, etc. - The requested analyzes. Despite this way of proceeding, laboratories must have controls that verify the state in which the samples arrive, and check whether they are unequivocally associated with their documentation. Most of the samples will be accepted and will become part of the laboratory's work list according to how it is established in each one of them. Samples showing any type of alteration must be checked according to various criteria to determine whether they are accepted or rejected. Specimens are typically rejected if:

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Unidentified specimens - Specimens obtained by non-invasive means must be retrieved. Those obtained by invasive means are processed with the prior authorization of the doctor. Delayed transport: defined as the time longer than recommended for each type of sample. They are only processed with prior authorization from the doctor, otherwise they must be repeated. Repeated samples: on the same day and specimens other than tissue or blood, require confirmation of the order by the doctor.

Once the sample has been extracted, there are criteria that may determine its non-acceptance: - Inadequate identification of the sample. - Inadequate volume taken. - Inappropriate additive used. - Inappropriate materials used for collection. - Hemolysis of the sample. - Inadequate measures used for transport or during transport (temperature, light, etc.). - Appearance of interfering elements that alter the results of the study. Analyzable substances Analyzable substances are closely linked to the type of sample obtained and the type of study requested. In short, there are very many substances that can be analyzed, continuously increasing with the different scientific advances. In general, analyzable substances are classified as: - Inorganic chemical substances. - Organic chemicals. - Cells and blood components. - Immune material. - Genetic material. In biological samples, the presence of microorganisms or parasites can be studied, this study will take place in the microbiology and parasitology laboratories, and cells or tissues that will be analyzed in the pathological anatomy laboratory. Samples for microbiological study Microbiological analysis is performed to detect the presence of microorganisms in a sample. It can be done by means of isolation and culture techniques or also by immunological techniques. The search targets bacteria (aerobic and anaerobic), fungi (in exudates), mycobacteria (in sputum), parasites, and viruses (in feces). A representative sample of the infectious process must be collected and in an adequate quantity to the request. An unrepresentative sample and / or a small amount of sample can be the cause of erroneous results.

Culture specimens should never be in contact with antiseptics or disinfectants and should be taken before starting any antibiotic therapy. Most of the time a previous antibiotic treatment alters the most careful microbiological investigation. Contact of the sample with commensal microorganisms of the patient should be avoided as far as possible using the appropriate aseptic procedure and measures. The samples must be sent in suitable containers: sterile, suitable means of transport and leak-proof closures. Samples that are not adequately protected or that arrive spilled or with stained containers will not be accepted. They should be sent as quickly as possible to the microbiology laboratory (within 2 h). If this is not possible, it is recommended to keep the samples (always as short as possible). Types of samples for microbiology Microbiological analyzes can be made of any sample, but the most common are: - Blood cultures. Study of the blood. - Urine culture. Study of urine. - Stool culture. Study of feces. - Studies of lesions on the skin or mucous membranes. Within these can be studied: • Abscesses. Accumulation of pus • Exudates. Liquids from inflammatory processes. • Vesicles. Elevation of the epidermis that has fluid inside. Preservation of samples for microbiology Speed is normally required when analyzing a sample destined for microbiology due to the possibility that the microorganisms present in the sample may be altered or it may be contaminated by elements foreign to it. Thus, there are several criteria to take into account to improve the conservation of the sample to be analyzed. -

Temperature: Bacteria normally resist low temperatures so a good way to preserve them is at 2-8ºC. But this is not the case with all of them. The following samples should not be refrigerated: ● blood ● CSFcultures ● Feces ● Samples in which the presence of anaerobes is to be determined...