The purpose of this study is to see if a blood test (D-dimer) is as precise as the CT scan for the detection of clots.

A pulmonary embolism is an obstruction of the blood vessels in your lungs usually due to a blood clot that travels to the lungs usually from the leg. Research has shown that the results of a specific blood test (D-dimer) can be used instead of a CT scan to diagnose clots. D-dimer is a valuable diagnostic marker in either detecting the presence of or monitoring the progress of blood clots. D-dimer assays have proven to be a beneficial diagnostic tool in the evaluation of patients with suspected pulmonary embolism (PE).

Inclusion Criteria:

• All patients evaluated in the urgent care center and determined to need with CT pulmonary angiogram to rule out pulmonary embolism based on signs and symptoms such as dyspnea, pleuritic chest pain, tachycardia, and/or pulse oxygen desaturation will be included.

Exclusion Criteria:

• Inability to obtain CT pulmonary angiogram secondary to lack of IV access, contrast allergy or lack of consent.
• CT pulmonary angiogram not done with routine protocol for rule out pulmonary embolism.
• Less than 21 years of age

Patients coming to MSKCC Urgent care unit