Because a missed PE could be potentially lethal, several researches reported that PE is both overinvestigated and overdiagnosed. The diagnostic gold standard for PE is the computed tomographic pulmonary angiogram (CTPA) and has been shown to have clear risks and other downsides. To limit the use of CTPA, two rules were recently reported to be safe to exclude PE: the PERC rule and the YEARS rule. PERC is an 8 item block of clinical criteria that has recently been validated to safely exclude PE in low risk patients. YEARS is a clinical rule that allow to raise the threshold of D-dimer for the order of CTPA. However, whether a modified diagnostic algorithm that includes these two rules combined could safely reduce imaging study use in the ED is unknown.

This is a non-inferiority, cluster cross-over randomized, international trial.

Each center will be randomized on the sequence of period intervention: 4 months intervention (MOdified Diagnostic Strategy: MODS) followed by 4 months control (usual care), or 4 months control followed by 4 months intervention with 1 month of "wash-out" between the two periods.

All centers will recruit adult emergency patients with a suspicion of PE.

In the control group (usual strategy), patients will be tested for D-dimer, followed if positive by a CTPA.

In the intervention group (MODS) :

All included patients will be tested with quantitative D-dimer. The MODS work-up will be based on YEARS rule :

- If all YEARS criteria are absent, the threshold of D-Dimer for ordering a CTPA will be raised.

If at least one criterion of YEARS is present, then the D-dimer threshold for ordering a CTPA will be as usual.

The diagnosis of Pulmonary Embolism (PE) is a crucial matter in the Emergency Department (ED). Because a missed PE could be potentially lethal, several researches reported that PE is both overinvestigated and overdiagnosed. The diagnostic gold standard for PE is the computed tomographic pulmonary angiogram (CTPA) and has been shown to have clear risks (allergic reaction, acute renal failure, delayed solid tumor) and other downsides such as prolonged ED stay and increased cost. To limit the use of CTPA, two rules were recently reported to be safe to exclude PE: the PERC rule and the YEARS rule.

PERC is an 8 item block of clinical criteria that has recently been validated to safely exclude PE in low risk patients.

YEARS is a clinical rule that allow to raise the threshold of D-dimer for the order of CTPA. However, whether a modified diagnostic algorithm that includes these two rules combined could safely reduce imaging study use in the ED is unknown.

The primary objective of this trial is to assess the safety of a modified diagnostic strategy (MODS) with the YEARS for patients in whom PE was not excluded by PERC score in the ED.

The primary endpoint is the failure percentage of the diagnostic strategy, defined as a diagnosed thrombo-embolic event at 3 month follow-up (either a PE or a deep venous thrombosis), among patients in whom PE has been initially ruled out.

The secondary outcomes try to assess the efficacy of the modified diagnostic strategy (MODS) in reducing order of irradiative imaging studies, ED length of stay, undue onset of anticoagulation regimen, hospital admission, hospital readmission, and mortality at 3 months.

To evaluate the efficacy of the modified diagnostic strategy to reduce overall 3-months total cost.

Secondary endpoints include:

• CTPA or V/Q scan
• Anticoagulant therapy administration
• Length of stay in the ED (hours)
• Admission to the hospital following ED visit.
• All causes re hospitalization at 3 months,
• Death from all causes at 3 months
• Diagnosed pulmonary embolism at 3 month follow-up excluding the isolated sub-segmental pulmonary embolism, among patients in whom PE has been initially ruled out
• PEPS score
• 3 months total cost and cost effectiveness

In the Modified diagnostic strategy (MODS), All included patients will be tested with quantitative D-dimer. The MODS work-up strategy will be based on YEARS rule, that included three criteria (hemoptysis, signs of DVT, PE is the most likely diagnosis)

- If all YEARS criteria are absent, the threshold of D-Dimer for ordering a CTPA will be raised at 1000 ng/ml.

If at least one criterion of YEARS is present, then the D-dimer threshold for ordering a CTPA will be as usual (500 ng/ml, or agex10 for patients aged 50 and over)

Group control :

All included patients will be tested with D-Dimer, the threshold for ordering a CTPA will be as usual (conventional age-adjusted threshold at 500 ng/ml, or agex10 for patients aged 50 and over).

Safely reducing the use of CTPA would be beneficial for the patients, by limiting their risk of associated adverse events and overdiagnosis of PE, and will also reduce their length of stay in the ED, which is associated with better outcomes. Furthermore, reducing supplemental investigations for patients with suspicion of PE may also reduce the cost of ED visits, which would be of great benefit in the context of increasingly resource stretched healthcare services.

Inclusion Criteria:

• Patient aged ≥ 18 years that presents to an ED
• With new onset of or worsening of shortness of breath or chest pain or syncope

Exclusion Criteria:

• Opposition to the participation to the study
• Anticipated inability to follow up at 3 month
• Other obvious cause than PE for chest pain, syncope or dyspnea
• High clinical probability of PE (estimated by the physician gestalt as > 50%) or low clinical probability and PERC negative patients
• Low clinical probability (estimated by the physician gestalt as < 15%) and no item of the PERC score (heart rate > 100, Sa02 < 95, unilateral leg swelling, hemoptysis, past history of thrombo-embolism, exogen estrogen intake, recent trauma or surgery, age ≥ 50)
• Acute severe presentation (clinical signs of respiratory distress, hypotension, SpO2<90%, shock)
• Concurrent anticoagulation treatment
• Current diagnosed thrombo-embolic event (in the past 6 months)
• Prisoners
• Pregnancy
• No social security
• Participation in another intervention trial

Yes, upon request, after approval by the primary investigator and clinical research platform of East Paris. For the purpose of IPD meta-analysis, or secondary analysis. Unidentifying data will be shared.