American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

Which of the following is a true anticoagulant?

1. Sodium citrate

2. Heparin

3. Sodium iodoacetate

4. EDTA

The correct answer is: Sodium citrate

Sodium citrate is recognized as a true anticoagulant because it directly chelates calcium ions in the bloodstream, which are essential for the coagulation cascade. By binding these calcium ions, sodium citrate effectively prevents blood from clotting during various laboratory procedures, such as in blood bank testing and coagulation studies. Its role as an anticoagulant involves maintaining the liquid state of blood samples, crucial for accurate laboratory analysis. The other substances listed have different functions. Heparin is also an anticoagulant but works through a different mechanism, enhancing the activity of antithrombin III to inhibit thrombin and factor Xa. Sodium iodoacetate is not an anticoagulant but is primarily used as a metabolic inhibitor in samples for certain biochemical assays. EDTA is another anticoagulant that works by chelating calcium, but it is more commonly used in hematology for preserving blood cell morphology rather than being classified as a true anticoagulant. Therefore, in this context, sodium citrate is the most clearly identified true anticoagulant used in laboratory settings.