Degradation of specimens is related to the conditions under which they were collected and stored and the assay to be done. Some specimens have been successfully assayed 30 years after collection, while others must be assayed immediately after collection because refrigerating for a significant period or even freezing for a short period will make the specimen unusable. If a commercial kit is being used for the assay, the kit instructions or the manufacturer's technical support should provide guidance on storage and stability. If the assay is under development by a research lab, the lab director will have to advise about these issues.


Keep in mind that if a specimen is collected for one purpose, the collection and storage procedures may not be appropriate for other assays. Anticipating possible future uses of a specimen is important so that informed consent to collect the specimen accurately reflects ultimate assays, and so that processing and storing methods provide the most flexibility for future assays.


One technique to assess degradation is to bank a large number of aliquots from a single specimen collection point (e.g., 10 aliquots of blood from one blood draw for several individuals), and assay single aliquots over time so that results can be compared across different storage periods.


Nano rainbow: nanocrystals under UV light

Courtesy: Shuming Nie,

Biomedical Beat, National Institute of General Medical Sciences

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