**Core Concept**
D-Dimer is a protein fragment produced when a blood clot dissolves. It is a sensitive marker for thrombosis and fibrinolysis, often used to diagnose conditions such as deep vein thrombosis (DVT) and pulmonary embolism (PE).

**Why the Correct Answer is Right**
D-Dimer is the most sensitive test for diagnosing thrombotic disorders, particularly DVT and PE. This is because D-Dimer levels are elevated in over 95% of patients with DVT and PE, making it an excellent screening tool for these conditions. The sensitivity of D-Dimer tests is due to the fact that they detect the presence of fibrin degradation products, which are generated when a blood clot dissolves.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while D-Dimer is a useful screening test, it is not the most sensitive test for diagnosing all types of thrombotic disorders.
**Option B:** This option is incorrect because while imaging studies such as ultrasound and CT scans are essential for diagnosing DVT and PE, they are not as sensitive as D-Dimer tests for initial screening.
**Option C:** This option is incorrect because while other biomarkers such as troponin and creatine kinase are important for diagnosing cardiac and muscle damage, they are not as sensitive as D-Dimer for diagnosing thrombotic disorders.

**Clinical Pearl / High-Yield Fact**
When interpreting D-Dimer results, it is essential to consider the patient's clinical context and risk factors for thrombosis. A high D-Dimer level in a patient with a low pre-test probability of thrombosis may indicate a false-positive result, while a low D-Dimer level in a patient with a high pre-test probability of thrombosis may indicate a false-negative result.

**Correct Answer:** D. D-Dimer is the most sensitive test for diagnosing DVT and PE.