To determine whether D-Dimer testing, using the MDA D-Dimer assay, can be used to simplify the diagnostic process for pulmonary embolism (PE). This will be assessed by performing a cohort study in 1000 patients with suspected PE.

To ascertain if an MDA D-Dimer result of less than 0.75 ug/mL FEU obviates the need for further testing and therapy in patients with suspected PE.

Prospective cohort study of 1000 patients in which those with a negative D-Dimer result undergo no further testing and are followed for 3 months for venous thromboembolism. Patients with a positive D-Dimer undergo standardized testing.

Inclusion Criteria:

• Age 18 years or older
• Suspected PE

Exclusion Criteria:

• Treatment with full-dose anticoagulants for 24 hours or more OR an ongoing requirement for anticoagulants
• Other tests for PE performed prior to eligibility assessment (e.g.other D-Dimer, V/Q scan, pulmonary angiogram, spiral CT, compression ultrasound, venogram).
• Cardiorespiratory instability requiring immediate performance of other tests to diagnose or exclude PE (i.e. inability to wait 30-60 minutes for MDA D-Dimer result)
• Comorbid condition limiting survival to less than three months
• Patient has been asymptomatic for seven days prior to presentation
• Current pregnancy
• Contraindication to contrast (e.g., allergy, renal failure).
• Geographic in accessibility which precludes follow-up
• Presence of central venous catheter (permanent or temporary, including PICC line) at the time of eligibility assessment