A sample is one or more parts taken from a larger system, such as a biological specimen or environmental material, that is intended to provide information about the whole【875887526410537†L178-L181】.
Explanation
In microbiology and laboratory science, a sample represents a portion of material collected for examination, measurement or culture. It may be drawn from a living organism (blood, serum, urine, tissue, swab), from food or water, or from environmental sources such as soil and air. Proper sampling aims to produce a representative fraction of the system so that results accurately reflect the state of the original population. The International Organization for Standardization (ISO 15189) defines a sample as one or more parts taken from a system to provide information about that system【875887526410537†L178-L181】. The type of sample, its volume and the method of collection all influence the reliability of test results.
Samples must be collected aseptically using sterile containers and instruments to avoid contamination, and they should be labeled with pertinent information (patient identity, date, site of collection). Transport conditions, such as temperature and time, are critical to preserve viability of microbes or stability of analytes. In research, sampling strategies can be random, stratified or targeted depending on study objectives. Replicate samples and controls are often processed to account for variability. Misleading results can occur if the sample is not representative, if it is mishandled, or if chain‑of‑custody documentation is inadequate. Thus, sampling is a foundational step in clinical diagnostics, food safety testing and environmental monitoring.
Types and Best Practices
- Clinical specimens: blood, serum, urine, cerebrospinal fluid, sputum, feces and swabs from throat, wound or nasopharynx.
- Environmental samples: water from rivers and drinking supplies, soil samples, air filters and surface swabs.
- Sampling methods: random sampling for unbiased estimation, stratified sampling to capture diversity, and composite sampling to reduce analysis costs.
- Handling considerations: use sterile equipment, maintain cold chain when necessary, avoid cross‑contamination and process samples promptly.
- Documentation: record sample source, time of collection and any pre‑analytical treatments to ensure traceability.
Whether for diagnosing disease, monitoring contamination or conducting research, the quality of laboratory data depends on the quality of the sample. Careful selection, collection and handling help ensure that the sample truly reflects the system under study.
Related Terms: Specimen, Sampling, Aliquot, Culture, Chain of custody.