A Complete Blood Count (CBC) is a super common blood test. It’s used to check for all sorts of things, from anemia to leukemia to inflammation. Getting the right blood sample is key for accurate results — and that starts with using the right blood collection tube for the CBC.
The lavender-top tube: EDTA and CBC
If you’re having a complete blood count (CBC) test, your blood will most likely be collected in a lavender-top tube. That’s because lavender-top tubes contain ethylenediaminetetraacetic acid, or EDTA, an anticoagulant that keeps the blood from clotting.
How EDTA works
EDTA binds to calcium ions in the blood, preventing the blood from clotting. This is important because a CBC needs to be performed on a whole blood sample. If the blood clots, the test results won’t be accurate.
How to handle the sample
Whole blood in EDTA tubes should be kept at room temperature or refrigerated if testing will be delayed. Samples are generally stable for up to 48 hours under either of those conditions. Keep in mind that refrigeration can sometimes cause the platelets to clump together.
Whether refrigerated or not, frozen, hemolyzed, or clotted samples are unacceptable for testing.
In Closing
When it comes to CBCs, using the correct lavender-top (EDTA) tube is essential for accurate results. Proper handling ensures the integrity of the specimen and reliable diagnostic information.