Bleeding time is prolonged in –
**Core Concept**
Prolonged bleeding time is indicative of a problem with primary hemostasis, which involves the initial formation of a platelet plug at the site of injury. This process is crucial for controlling bleeding in the early stages after injury.
**Why the Correct Answer is Right**
The correct answer is related to a deficiency in von Willebrand factor (VWF), a key protein involved in primary hemostasis. VWF is essential for the adhesion of platelets to the site of injury, allowing them to aggregate and form a platelet plug. A deficiency in VWF, as seen in von Willebrand disease, leads to impaired platelet function and prolonged bleeding time.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because bleeding time is a measure of primary hemostasis, not coagulation. Disorders of coagulation, such as hemophilia, would affect secondary hemostasis and be detected by clotting time tests, not bleeding time.
**Option B:** This option is incorrect because platelet count is not the primary determinant of bleeding time. While a low platelet count (thrombocytopenia) can affect bleeding time, it is not the most common cause of prolonged bleeding time.
**Option C:** This option is incorrect because platelet function disorders, such as Glanzmann thrombasthenia, can affect bleeding time. However, this is not the most common cause of prolonged bleeding time.
**Clinical Pearl / High-Yield Fact**
A classic exam trap is to confuse bleeding time with clotting time. Remember that bleeding time is a measure of primary hemostasis, while clotting time is a measure of secondary hemostasis.
**Correct Answer:** C. Platelet function disorders.