Modified Strategy to Safely Rule Out Pulmonary Embolism in the Emergency Department

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.