Pulmonary Embolism in Patients with Unexplained Exacerbation of Chronic Obstructive Pulmonary Disease: Prevalence and Risk Factors

BACKGROUND: Diagnosis of pulmonary embolism (PE) is difficult in patients with chronic obstructive pulmonary disease (COPD) and exacerbation. OBJECTIVE: To evaluate PE in patients with COPD and exacerbation of unknown origin and explore factors associated with PE. DESIGN: Prospective cohort study. SETTING: University-affiliated hospital in France. PATIENTS: 211 consecutive patients, all current or former smokers with COPD, who were admitted to the hospital for severe exacerbation of unknown origin and did not require invasive mechanical ventilation. MEASUREMENTS: Spiral computed tomography angiography (CTA) and ultrasonography within 48 hours of admission and assessment of the Geneva score. Patients were classified as PE positive (positive results on CTA or negative results on CTA and positive results on ultrasonography) or PE negative (negative results on CTA and negative results on ultrasonography or negative results on CTA and no recurrence of PE at follow-up 3 months later). RESULTS: 49 of 197 patients (25% 95% CI, 19% to 32%) met the diagnostic criteria for PE. Clinical factors associated with PE were previous thromboembolic disease (risk ratio, 2.43 CI, 1.49 to 3.94), malignant disease (risk ratio, 1.82 CI, 1.13 to 2.92), and decrease in PaCO2 of at least 5 mm Hg (risk ratio, 2.10 CI, 1.23 to 3.58). A total of 9.2% (CI, 4.7% to 15.9%) of patients with a low-probability Geneva score received a diagnosis of PE. An exploratory analysis suggested that substituting malignant disease for recent surgery in the Geneva score might improve its performance in excluding PE in this sample who were more likely to have malignant disease than to have had recent surgery. However, this improvement seems insufficient to exclude PE with enough certainty to withhold therapy for low-risk patients on the basis of the modified score. LIMITATIONS: This study was done in only 1 center. Patients with COPD requiring invasive mechanical ventilation in the intensive care unit were not included. The upper bound of the 95% CI for the low probability of PE according to the Geneva score is too high to rule out PE. The classification of COPD exacerbation of unknown origin was based on the clinician's assessment, not on a standard evaluation for all patients. CONCLUSION: This study showed a 25% prevalence of PE in patients with COPD hospitalized for severe exacerbation of unknown origin. Three clinical factors are associated with the increased risk for PE. The Geneva score and the modified Geneva score should be prospectively evaluated in patients with COPD.