What could indicate a factor deficiency in a patient?

The identification of a factor deficiency is often assessed through coagulation studies, particularly by evaluating the activated partial thromboplastin time (aPTT). A prolonged aPTT indicates a potential issue with the intrinsic pathway of the coagulation cascade, which involves a variety of clotting factors (such as factors VIII, IX, and XI).

When mixing studies are performed, the patient's plasma is mixed with normal plasma. If the aPTT corrects after this mixing, it suggests that the prolonged aPTT is due to the presence of an inhibitor rather than a deficiency of a coagulation factor. However, if there is no correction of the aPTT after mixing, it indicates that the issue may be due to a factor deficiency. This is because the normal plasma added cannot compensate for the lack of the deficient factor(s) present in the patient's plasma. Therefore, a prolonged aPTT that does not correct with mixing is indicative of a potential factor deficiency, making this the correct choice.

The other options are not indicative of a factor deficiency; for example, a correction in aPTT after mixing suggests an inhibitor rather than a factor deficiency, while an elevated platelet count and normal fibrinogen levels do not directly correlate with the presence of