Phlebotomy – Order of Draw Practice Test

The correct answer pertains to the importance of proper mixing in the coagulation process for blood samples collected in light blue top tubes, which typically contain sodium citrate as an anticoagulant. Inverting the tube three to four times ensures that the anticoagulant is thoroughly mixed with the blood sample, preventing coagulation and allowing for accurate laboratory analysis.

Sodium citrate works by binding calcium in the blood, and if the sample is not adequately mixed, it may lead to clot formation, which could compromise the test results. This is particularly crucial for tests like prothrombin time (PT) and activated partial thromboplastin time (aPTT), where accurate measurement of clotting times is essential. Therefore, following the recommended inversion count helps maintain sample integrity and ensures reliable results during testing.