How many times should EDTA tubes be inverted after collection?

• A. 1-2 times
• B. 8-10 times
• C. 15-20 times
• D. 5-7 times

Answer: (B)

Mixing the blood with EDTA right after collection is essential to prevent clotting and to keep cell morphology accurate for hematology testing. EDTA works by binding calcium, so it needs to be distributed evenly throughout the specimen to stop coagulation everywhere, not just in part of the tube. A moderate number of gentle inversions ensures the additive coats all cells and mixes well without causing excessive agitation. If mixing is too light, the additive won’t be distributed, and microclots can form, skewing results like the CBC and platelet counts. If mixing is excessive, it can cause foaming or mechanical damage to cells, which also can distort results. Following a standard mid-range practice gives reliable, representative results without risking artifacts.