blood sample storage: 3 tips for managing sample storage effectively
For specimen integrity and accurate test results, blood samples must be stored in specific ways. The way the blood is initially taken and how it's transported and stored affect its long-term viability.
Sample Size: Take a large enough sample of blood
Each volume of blood taken should be enough to run two - either separate or duplicate - of the desired tests. If a sample is too small, a result can't be confirmed or repeated. A good rule of thumb is to collect between 2 and 2.5 times the volume that the test requires.
Blood should be tested very soon after it's drawn, usually within about four hours. Serum samples should be separated from whole blood within two hours of the blood draw. Additives such as a clot accelerator, anticoagulant, or heparin might be used, depending on the testing need. Each additive affects blood sample testing and storage in different ways. For example, hematology procedures often require the blood to remain in the tube until the anticoagulants stabilize.
Temperature: Maintain appropriate sample temperature
Depending on the sample use, one of three temperatures will typically be specified for blood sample storage: room temperature, refrigerated, or frozen. Room temperature is specified as between 15 and 30°C; refrigeration temperature is between 2 and 10°C; frozen temperature is at or below 20°C.
Blood used for certain molecular genetic tests can remain stable for many days, with a wide range of acceptable temperature. DNA remains stable at room temperature for up to a month, but because live blood cells begin dying within two days, samples should be cultured or frozen in liquid nitrogen for future use.
Length of Storage: Make sure conditions are right
Blood banks consider six weeks to be the "shelf life" of blood, but a study from Johns Hopkins University has shown that after three weeks, red blood cells are less effective at delivering oxygen-rich cells throughout the body. Blood stored longer than three weeks becomes less flexible and less able to fit in the body's smallest capillaries.
Depending on the blood's future use, longer storage without refrigerated or frozen temperatures can jeopardize its viability. For example, if stored blood is used in a transfusion, the blood never regains the flexibility that it lost after the three-week mark unrefrigerated in storage.
Given the relatively rapid degradation of blood after it's drawn, all samples should be promptly tested, refrigerated for short-term storage, and frozen for long-term storage.
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