Question 68

Silica promotes clot formation.

Silica is a tube additive that promotes clot formation by providing a surface for platelets to adhere to, which is crucial in the coagulation process.

A) Heparin

Heparin is an anticoagulant that inhibits clot formation by enhancing the activity of antithrombin III. It prevents the conversion of prothrombin to thrombin, thereby interfering with the clotting cascade.

B) Oxalate

Oxalate acts as an anticoagulant by binding calcium ions, which are essential for blood coagulation. By removing calcium from the clotting process, oxalate effectively prevents clot formation.

C) Citrate

Citrate is another anticoagulant that works by chelating calcium ions, similar to oxalate. This action inhibits the clotting process and prevents clot formation during blood collection and storage.

D) Silica

Silica is a clot activator that enhances the coagulation process by providing a surface for platelets to aggregate and initiate the clotting cascade. This makes it effective in promoting clot formation in blood samples.

Conclusion

Silica is definitively the correct answer as it actively promotes clot formation, unlike the other options which are all anticoagulants designed to inhibit the clotting process. Heparin, oxalate, and citrate all work to prevent coagulation, while only silica facilitates the necessary conditions for clot development.