Question 9

Silica promotes clot formation.

Silica is a tube additive that promotes clot formation by activating the coagulation cascade. It is commonly used in serum separator tubes to facilitate the collection of serum for laboratory tests.

A) Heparin

Heparin is an anticoagulant that prevents clot formation by inhibiting thrombin and factor Xa. Therefore, it does not promote clot formation but rather works to keep blood in a liquid state, making it incorrect in the context of the question.

B) Oxalate

Oxalate acts as an anticoagulant by binding calcium ions, which are necessary for the clotting process. This means that oxalate inhibits clot formation, making it an incorrect choice for promoting clotting.

C) Citrate

Citrate also functions as an anticoagulant by chelating calcium ions, thereby preventing the clotting cascade from occurring. Because of this mechanism, citrate does not promote clot formation and is therefore not the correct answer.

D) Silica

Silica is specifically known for its ability to promote clot formation by serving as a surface that activates platelets and encourages the coagulation process. This makes silica the correct answer as it directly facilitates the formation of clots in blood samples.

Conclusion

Silica is the only option among the choices that actively promotes clot formation, while heparin, oxalate, and citrate serve to inhibit this process. Understanding the role of these additives is crucial in laboratory settings, particularly when collecting blood samples for testing that require serum. Thus, silica is definitively the correct answer.