Question 51

Silica promotes clot formation.

Silica is an additive that facilitates the clotting process by providing a surface for platelets to adhere to and aggregate, thereby promoting the formation of a clot.

A) Heparin

Heparin is an anticoagulant that prevents clot formation by inhibiting thrombin and factor Xa, thus serving to keep blood fluid rather than promoting clotting. It is commonly used to prevent thrombosis, making it incorrect in the context of promoting clot formation.

B) Oxalate

Oxalate acts as an anticoagulant by precipitating calcium ions, which are essential for the coagulation cascade. This property prevents clot formation rather than promoting it, thus making this option incorrect.

C) Citrate

Citrate is another anticoagulant that binds calcium, thereby inhibiting the clotting process. Its primary role is to prevent clotting in blood samples, which disqualifies it from being a promoter of clot formation.

D) Silica

Silica is specifically designed to promote clot formation by providing a surface for platelets to adhere, leading to aggregation and clot development. This characteristic aligns perfectly with the question's requirement for a tube additive that encourages clotting.

Conclusion

Silica is the only additive among the options that actively promotes clot formation, making it the definitive correct answer. In contrast, heparin, oxalate, and citrate all serve to inhibit clotting through various mechanisms, confirming that they do not meet the criterion set by the question.