Which lab test is commonly associated with pulmonary embolism (PE)?

Elevated D-dimer levels are commonly associated with pulmonary embolism (PE) because D-dimer is a fibrin degradation product that is released when a blood clot dissolves. In the context of PE, when a thrombus (blood clot) forms and subsequently embolizes to the pulmonary circulation, the body responds by activating the fibrinolytic system, leading to increased levels of D-dimer in the bloodstream as clots are broken down.

While a D-dimer test is not specific and can be elevated in various conditions, its utility lies in its ability to help rule out the diagnosis of PE when levels are normal. In clinical practice, elevated D-dimer levels suggest the presence of a thrombotic process, prompting further investigation for conditions like PE, particularly in patients with a moderate to high pre-test probability of having the condition.

In contrast, other lab tests listed, such as increased platelet count, prolonged PT and aPTT, or low hemoglobin levels, do not have a direct association with pulmonary embolism. Increased platelet counts may be seen in various other conditions, prolonged PT and aPTT could suggest coagulopathy or other disorders, and low hemoglobin levels typically indicate anemia rather than a direct link to embolism.