Introduction to Specimen Extraction
The number of research and clinical studies being conducted to help improve screening procedures, diagnostic tests, therapies, and prognosis is rapidly increasing. This means tissue samples or biospecimens such as fresh frozen tissue and formalin-fixed paraffin-embedded (FFPE) blocks are of great value researchers. Obtaining high-quality samples is the first step towards credible data and testbale results. This is why suppliers of biospecimens should aim to collect, maintain, and disseminate the best biospecimens possible. High-quality samples are those that resemble the biology of the donor before its removal from the host. Once removed, the specimen may change based on the environment. Such things as exposure to different chemicals or environmental factors during the collection or storage procedure are all things that can negatively affect the sample.
Pre-analytic variables are factors that affect the collection, processing, and storage conditions that impact the integrity of the biospecimen before their removal from the host. Examples include, but are not limited to:
a) Donor Physiology
This includes things such as the health of the donor, consumption of food, beverages or medications before the collection of the specimen, time of day the specimen was collected, and the type of anesthesia used. In female donors, even the time of their menstrual cycle can affect the downstream analysis. This stresses the importance of collecting this information from donors to decrease variability between samples.
b) Collection Practices
It is important to maintain uniformity during the removal and collection of specimens from donors as different methods can affect the quality of the biospecimens. These specimens should also be preserved very quickly after removal from the donor. Newer preservation methods should be considered as they can allow for better and more accurate preservation of the biospecimen. Some of the factors that should be considered during biospecimen collection include, inter alia:
The site of collection
Type of anesthesia used
Warm ischemia time
Use of stabilizing agents
Types of fixatives used
Exposure time to fixatives
The temperature for maintaining biospecimens.
All the above factors can affect the stability and degradation of molecules in the samples. Annotation of the biospecimens should include the donor’s information. This data should be recorded and maintained in a database. Handling of biospecimens should also be optimized to reduce molecular changes that may occur due to processing activities.
Analytic variables are factors that affect the performance of a testing procedure. To reduce errors, some of the following factors should be considered:
Always use validated assays whenever possible.
Train technical staff regarding the standard operating procedure.
Use uniformed reagents.
Use the proper type and number of control samples.
If possible, randomization should be applied.
Use standardized methods during the documentation and interpretation of results.
Biospecimen Collection and Reference Ranges
The specimens collected has to be appropriate for the clinical study and downstream applications that will be used in the research. Biospecimens should be examined by a qualified histopathologist to ensure quality and accuracy. Reference ranges should be used to ensure that any deviation from the reference range can be accurately detected. This is due to the reason where disease can be defined as a deviation from normal variation. This means the diagnosis of the disease depends on the scope of normal variation. All reagents should be quality controlled, so it is fit to be used in the assay. The standard operating procedures (SOPs) should be reproducible with control biospecimens that have a range of anticipated assay values. Poorly handled biospecimens tend to produce erroneous test results due to molecular changes.
The following practices should be applied to all types of biospecimens:
Follow standard protocols when storing biospecimens to maintain quality. Personnel should record the conditions for storage, deviations from SOPs, temperature, equipment failures, and thaw / refreeze episodes. It is essential to validate storage equipment, maintain back up equipment, and identify “hot spots” in the freezer.
Store specimens in a stabilized state.
Avoid unnecessary thawing and refreezing.
Follow protocols if thawing and refreezing are necessary.
Inventory tracking is desirable as it helps reduce the disruption of the environment during retrieval of samples.
Consider the length of storage, type of biospecimen, biomolecules of interest, and study goals when selecting storage temperature for samples.
Use appropriate storage vessels and ensure stability under storage conditions. The proper storage vessel can prevent sample loss and reduce costs of storage and retrieval of biospecimens.
Choice of labels and printing should include the consideration of long-term storage conditions.
Protection for personnel such as face shields and gloves should be worn.
Each specimen should have a unique identifier that is clear, affixed, and able to endure the storage conditions.
Automated alarms that monitors the storage equipment with the capability to warn personnel when equipment failure occurs should be in place.
An alternative power source and other backup equipment should activate automatically if there is equipment failure.
SOPs to routinely test equipment failure, backup equipment, and other emergency situations should be available.
Specimens should only be available to authorized personnel.
Ensure appropriate shipping conditions and documentation.
Biospecimen collection, processing, storage, retrieval, and dissemination. National Cancer Institute. Accessed 9/18/2018.https://biospecimens.cancer.gov/bestpractices/to/bcpsrd.asp