The activated partial thromboplastin time (APTT) serves as a screening procedure for which plasma factor deficiencies?

The activated partial thromboplastin time (APTT) is a crucial laboratory test used to assess the intrinsic pathway of coagulation, which identifies the function of factors involved in this pathway. The APTT primarily screens for deficiencies in several specific plasma clotting factors.

The correct answer includes factors XII, IX, XI, VIII, X, V, II, and I. This comprehensive list indicates that APTT tests for multiple intrinsic pathway factors, as well as the common pathway factors, including prothrombin (factor II) and fibrinogen (factor I). Each of these factors plays a vital role in the coagulation cascade, influencing the time it takes for blood to clot. If any of these factors are deficient or dysfunctional, the APTT will be prolonged, indicating a potential bleeding disorder.

Though other choices may list some of these plasma factors, they do not encompass the full range of factors that the APTT assesses. The inclusion of all relevant factors is essential for a complete understanding of the coagulation process and the ability to detect various bleeding disorders effectively.