In the YEARS study, clinical pretest probability scoring with three of the original Wells criteria (i.e., YEARS items)—(1) clinical signs of DVT, (2) hemoptysis, and (3) PE is the most likely diagnosis—was applied to inpatients and outpatients with suspected PE.PE was excluded if patients had zero YEARS criteria and D-dimer <1000ng/mL or≥ 1 YEARS criteria and D-dimer <500ng/mL; otherwise, com­puted tomography pulmonary angiography (CTPA) was pursued. Use of YEARS criteria and clinical probability-adjusted D-dimer resulted in a <1% risk of VTE at 3months and a 14% decrease in CTPA testing among patients of all ages compared to the use of standard Wells criteria and D-dimer <500ng/mL [107].

CTPA is the gold standard for conrming the presence of PE.Intravenous radi­opaque contrast allows for the visualization and detection of lling defects in the pulmonary arteries on computed tomography. For patients with a low or intermedi­ate probability of PE, guidelines suggest that a negative CTPA is adequate to exclude PE.However, the negative predictive value is low for patients with high clinical probability [59]. Figure 8.1 shows lling defects (pulmonary thromboemboli) in bilateral pulmonary arteries, which are consistent with acute PE.

PE.Home treatment may be appropriate for patients with a low risk of PE-related death, no serious comorbidities or concomitant conditions requiring hospitalization, and no barriers to compliance with outpatient treatment. The pharmacist clinician is poised to provide anticoagulation counseling, address patient questions, and relay signs and symptoms that would warrant re-presentation back to the ED.

For patients appropriate to receive home treatment, rapid anticoagulation with a direct oral anticoagulant (DOAC) is preferred over inpatient treatment with 5days of a parenteral anticoagulant [59, 99]. Notably, certain oral anticoagulants including dabigatran and edoxaban require initial treatment with a parenteral anticoagulation for a minimum of 5days prior to transitioning to the oral agent. Vitamin K antago­nists (VKAs) such as warfarin require an overlap with a parenteral anticoagulant upon initiation until a therapeutic INR between 2.0 and 3.0 is achieved, typically for a minimum of 5days. In contrast, apixaban and rivaroxaban can be initiated imme­diately following the PE diagnosis as the sole agent. Apixaban and rivaroxaban require higher initial doses when initiating upon diagnosis of a PE according to the FDA-approved package insert, for 7 and 21 days, respectively [59, 77, 99]. The choice of oral anticoagulant depends on patient-specic factors such as renal func­tion, affordability, drug-drug interactions, and other comorbidities such as antiphos­pholipid antibody syndrome. Frequency of dosing (e.g., once daily or twice daily) is an important factor for patients with concern for medication compliance. For a patient who otherwise has no contraindications, the use of a DOAC is preferred over vitamin K antagonists (VKA) [77]. Additional considerations for oral anticoagu­lants are listed in Table8.7.

Table 8.8 outlines the initiation and maintenance phases of each oral anticoagu­lant. Patients not eligible for rapid anticoagulation with apixaban or rivaroxaban will require initial management with a parenteral anticoagulant. Subcutaneous injections of low-molecular-weight heparin (LMWH) or fondaparinux can be administered at home with appropriate patient education. The choice of anticoagu­lant for specic populations, such as those experiencing pregnancy or cancer, is discussed further in forthcoming sections.