ensuring blood sample viability and understanding their shelf life and storage guidelines

The journey of a blood sample—from the moment it's collected to its analysis in a laboratory—is critical for ensuring accurate diagnostic results. The way blood samples are collected, transported, stored, and processed significantly impacts their viability and the integrity of the test results obtained.

Importance of Correct Blood Sample Volume

For accurate analysis and test reliability, collecting the correct volume of blood is crucial:

• Optimal Volume: Blood samples should be substantial enough to conduct two separate tests, either duplicate or distinct, of the intended analyses. Typically, blood draws collect approximately 2 to 2.5 times the required test volume, ensuring test repeatability and confirmation.

• Waste Reduction: Although traditional blood draws often collect excess blood, much of which is ultimately discarded, dried blood testing generally requires much smaller volumes, minimizing waste and discomfort.

Proper Labeling of Samples

Proper labeling of blood samples, whether tubes, devices, or filter papers, ensures accurate tracking and identification:

• Identification Methods: Samples can be labeled with pre-printed labels containing the individual's name and patient identification number or with unique barcodes incorporating the individual's pertinent information.

• Home Collection: For at-home self-collected samples using finger-stick microsampling, it is essential to label the device or filter paper before it leaves the individual's possession to ensure proper matching and tracking.

Blood Sample Storage Guidelines

Adhering to proper storage conditions is essential for maintaining sample integrity. Blood sample storage temperatures vary based on intended use:

• Room Temperature: 15° to 30°C

• Refrigerated: 2° to 10°C

• Frozen: At or below -20°C

Blood samples intended for specific molecular genetic tests can remain stable for several days across varying temperatures. DNA, for instance, remains stable at room temperature for up to a month. Conversely, live blood cells begin losing viability within two days unless cultured or frozen using liquid nitrogen for prolonged storage.

Shelf Life of Whole Blood

Whole blood samples, commonly referred to as "wet blood," have limited shelf life:

• Standard Shelf Life: Six weeks is typically the maximum shelf life for blood donations intended for transfusions.

• Optimal Effectiveness: After three weeks, blood's efficiency in oxygen delivery significantly decreases, affecting its ability to navigate the smallest capillaries, especially if not properly refrigerated.

• Flexibility and Viability: Blood stored unrefrigerated beyond three weeks permanently loses flexibility, underscoring the need for swift testing or appropriate storage methods such as refrigeration or freezing.

Maintaining Wet Blood Sample Viability

Specific guidelines outline the timeframe for processing wet blood samples:

• Room Temperature Stability: Samples kept at room temperature (approximately +15°C to +30°C) must be analyzed within eight hours.

• Refrigerated Storage: Samples stored between +2°C and +8°C remain viable for up to seven days.

• Frozen Storage: If analysis occurs beyond seven days, samples must be frozen at temperatures between -15°C and -20°C.