Question 68

Silica promotes clot formation.

Silica is an additive that enhances the clotting process in blood samples, making it an effective agent for promoting clot formation.

A) Heparin

Heparin is an anticoagulant that prevents clot formation by inhibiting thrombin and factor Xa. It is commonly used to maintain blood fluidity and is not a promoter of clot formation, making this option incorrect.

B) Oxalate

Oxalate is a compound that acts as an anticoagulant by precipitating calcium ions, which are necessary for the clotting process. Therefore, it does not promote clot formation, rendering this option incorrect.

C) Citrate

Citrate is another anticoagulant that binds to calcium ions in the blood, thus preventing clotting. Its primary function is to inhibit the clotting cascade, making this option incorrect as well.

D) Silica

Silica acts as a clot activator by providing a surface for platelets to adhere and aggregate, facilitating the clotting process. This property confirms that silica is indeed a promoter of clot formation, making this option correct.

Conclusion

Silica is the only additive among the options that actively promotes clot formation, while heparin, oxalate, and citrate all function as anticoagulants that prevent clotting. Therefore, the correct answer is definitively D, as it aligns with the mechanism of enhancing clot formation in blood samples.