NHA Phlebotomy Certification Practice Exam

In what situation can EDTA tubes be processed up to 12 hours after collection?

1. If they are frozen

2. If they are kept at room temperature

3. If they are refrigerated

4. If they are mixed immediately after collection

The correct answer is: If they are refrigerated

EDTA tubes, which are used primarily for hematology tests, help to preserve the shape and function of blood cells by preventing clotting. When blood specimens are collected in EDTA tubes, it is essential to process them appropriately to ensure the integrity of the samples. Processing EDTA tubes by refrigerating them allows the samples to be stable for an extended period, up to 12 hours, without significantly affecting the results. Refrigeration slows down any metabolic processes that may occur in the blood cells and preserves the morphology of the cells, which is crucial for accurate testing results. This is particularly important in tests such as complete blood counts (CBC), where the morphology and quantity of blood cells are critical for diagnosis. Keeping the samples cold helps to maintain the viability of the cells, thus ensuring that the analysis will yield reliable and valid data. In contrast, other scenarios, such as freezing or keeping the tubes at room temperature, can lead to cell lysis, changes in cellular composition, or even alterations in the biochemical properties of the blood, which would adversely affect test outcomes. Immediate mixing of the sample after collection is important to prevent clotting but does not substitute for proper temperature management regarding the timeline for processing.