4 Specimen Storage and Stability
Learn how to preserve specimen integrity, follow test-specific storage and handling requirements, and assess whether a specimen remains acceptable for analysis.
Why specimen preservation matters
A specimen can change between collection and measurement. Cells may continue consuming or releasing substances, proteins and nucleic acids may degrade, microbes may multiply or die, and light, temperature, time, or evaporation may alter measured concentrations. These changes can produce results that no longer reflect the patient’s condition.
The goal is to preserve the specimen’s suitability for the specific test requested. A specimen may be acceptable for one test but not another, so storage and handling requirements must be checked for each test rather than applied universally.
Choosing storage conditions
Use the current test directory, collection-device instructions, and receiving laboratory requirements to determine the specimen type, container, temperature, maximum holding time, and any required preservative. Terms such as room temperature, refrigerated, and frozen may refer to different defined ranges at different laboratories.
Room temperature: Appropriate for some tests, but not a default for all specimens. Protect specimens from excessive heat or cold.
Refrigerated: Often slows cellular activity and degradation when specified. Refrigeration can affect some analytes or cause precipitation, so do not chill specimens automatically.
Frozen: Used when longer-term preservation is required or when the test specifically requires a frozen specimen. Use the required temperature and container. Avoid repeated , which can damage some analytes.
Protected from light: Wrap the specimen or use an appropriate light-protective container when required, because some analytes are light-sensitive.
: Use only the specified preservative or transport medium and the correct container; a preservative can interfere with other tests.
Urine requirements vary by analyte and test method. Some urine analytes require refrigeration, while others require freezing, acidification, or protection from light. A timed urine collection may need to remain cool throughout collection and be mixed before an aliquot is prepared.
and time limits
is the period during which a specimen remains suitable for a test under specified conditions. It depends on the analyte, specimen type, collection tube or preservative, temperature, and whether processing has occurred. A test directory may specify different limits for room-temperature, refrigerated, and frozen specimens.
Record collection and processing times when required, and transport specimens promptly. If a delay or occurs, document it and check the test-specific acceptance criteria. Do not assume cooling or freezing can restore a specimen after its limit has been exceeded.
Handling and processing specimens
Before analysis, keep each specimen in its approved, correctly labeled container and maintain the required temperature. Prevent leakage, evaporation, contamination, and unnecessary light exposure, and handle specimens using appropriate precautions. During transport, use secure, leak-resistant packaging and the temperature controls required by the receiving laboratory.
When processing blood, follow the collection tube’s instructions for clotting and . conditions are not interchangeable: the required force and duration depend on the tube, specimen, and procedure. After , inspect the specimen and separate serum or plasma from cells when required by the test instructions. Continued contact with cells can change some measurements; avoid disturbing the cell layer or transferring cells into an aliquot.
, processing, transport, and storage are connected factors in specimen quality. Keep collection and processing requirements in view throughout these steps.
Post-analysis storage and specimen acceptance
After analysis, retain, refrigerate, freeze, or discard the remaining specimen according to laboratory procedure and test-specific requirements. When aliquots are needed, use appropriate labeled containers and minimize unnecessary transfers and . Store specimens securely and monitor storage equipment as required by laboratory policy.
For example, a blood sample arrives after a transport delay. The requested test requires separated plasma, but the sample remains in contact with cells. The technologist checks the test directory for the allowed processing delay and specimen , documents the arrival condition, and decides whether the sample remains acceptable for that test. Refrigerating it at that point is not assumed to reverse changes that may already have occurred.
Assess separately for each requested test. Document delays or deviations and determine whether the specimen meets the applicable acceptance criteria before analysis.