Citrate tubes have an inversion exception of how many times?

• A. 2
• B. 3-4
• C. 5
• D. 8-10

Answer: (B)

Citrate tubes must be mixed with the blood to distribute the anticoagulant evenly and maintain the correct blood-to-anticoagulant ratio, so clotting is prevented from occurring after collection. Inverting the tube gently a small number of times achieves this mixing without creating bubbles or causing sample damage. If you invert too few times, the citrate may not mix thoroughly and clotting or inaccurate coagulation results can occur. If you invert too many times, foaming or hemolysis can affect test accuracy. The standard practice is a brief series of gentle inversions to ensure uniform distribution, which corresponds to three to four gentle inversions.