Risk factors for pulmonary embolism in patients preliminarily diagnosed with community-acquired pneumonia: a prospective cohort study

D-dimer levels are increased in patients with acute pulmonary embolism (PE). However, D-dimer levels are also increased in patients with community-acquired pneumonia (CAP). The aim of this prospective cohort study was to examine the incidence and clinical features of patients preliminarily diagnosed with CAP and with increased D-dimer levels, and who finally were diagnosed with PE. Patients diagnosed with CAP and hospitalized in the Respiratory Department of the Tenth People's Hospital Affiliated to Tongji University between May 2011 and May 2013 were enrolled. D-dimer levels were measured routinely after admission. For patients with increased D-dimer levels, those suspected with PE underwent computed tomography pulmonary angiography (CTPA). A total of 2387 patients with CAP was included: 724 (30.3 %) had increased D-dimer levels (median of 0.91 mg/L). CTPA was performed for 139 of the 724 patients (median D-dimer levels of 1.99 mg/L). Among the 139 patients, 80 were diagnosed with PE, and 59 without PE; D-dimer levels were 2.83 and 1.41 mg/L, respectively (p < 0.05). Multivariate analysis showed that age, coronary heart disease, chronic obstructive pulmonary disease (COPD), lower limb varicosity, chest pain, shortness of breath, hemoptysis, fever, and increased levels of troponin I were independent risk factors for PE. Presentation of PE and CAP are similar. Nevertheless, these results indicated that for hospitalized patients with CAP and elevated D-dimer levels, PE should be considered for those > 60 years; with CHD, COPD, or lower limb varicosity; with chest pain, shortness of breath, hemoptysis, increased troponin I, or low fever.