In this study, a new, non-invasive method for diagnosis of pulmonary embolism (PE) will be tested. In pre-clinical studies, we have identified 151 putative biomarkers for pulmonary embolism in the exhaled breath condensate (EBC). These biomarkers needs validation/consolidation in a clinical setting before further test of this new diagnostic method.

The study will compare the protein profiles of EBC collected from patients admitted to the department of cardiology with suspected pulmonary embolism and controls with same age (within a range of 10 years) and gender from the outpatient clinic awaiting elective cardiovascular surgery. The main-outcome (i.e. means of the relative amounts of specific proteins in the EBC samples) will be compared by unpaired t-tests after assessment of normality and standard deviations within the three groups (PE confirmed, PE suspected but not confirmed and controls). Furthermore, sensitivity and specificity will be calculated for relevant proteins. The results from analysis of EBC samples from the patients and controls will be compared with results from the porcine model in order to confirm and reduce the number of putative biomarkers for PE. Blood samples (i.e. excess plasma from routine blood samples drawn as a part of routine diagnostic work-up) from the study participants will be stored for standardization of the putative markers and verification and supplementing analysis of the EBC markers. In order to qualify the most suitable markers and substrates for standardization, the analysis of the EBC samples must be completed before the blood samples can be analyzed. Only biochemical, no genetic analysis will be conducted.

Inclusion Criteria - Suspected/confirmed PE patients:

• Admitted to the emergency department with initial diagnosis of PE, visited to the Department of Cardiology at Aalborg University Hospital.
• Are conscious and able to understand the given study information.
• Possess legal capacity.
• Age above 18 years.
• Informed, signed consent is obtained.
• Clinically stable, which is defined as patients with stable blood pressure and not in need for other treatments .
• No need for organ support, which comprises need for vasopressors or inotropes, mechanical ventilation, extra corporal circulation or renal replacement therapy.

Inclusion Criteria - Controls:

• Patients as the PE patients, but where the diagnosis of PE is rejected.

The rest of the control persons will be recruited as described:

• Patients who are going to have elective procedures at the Department of Cardiology, Aalborg University Hospital.
• Same gender and age (within a 10-year range) as an included PE patient.
• Are conscious and able to understand the given study information.
• Possess legal capacity.
• Age above 18 years.
• Informed, signed consent is obtained.

Exclusion Criteria:

• Active malignant disease (i.e. ongoing anti-cancer therapy or palliation).
• Current smokers

It is expected that

• 40 patients with confirmed PE,
• 40 patients with suspected PE, but where diagnostic work-up did not confirm PE and
• 40 healthy controls

will be included in the study over a six-month period.