In this study, we showed that the frequency of PE was 25% in a series of 197 consecutive patients with COPD referred for severe exacerbation of unknown origin. This is similar to the value of 27% reported in the Geneva study (1). In contrast with the clinical scores recently developed for diagnosing PE in unselected patients, the Geneva score (1) and the score reported by Wells and colleagues (2), we found that only 3 factors predicted PE: history of thromboembolism, malignant disease, and a decrease in Paco2 of at least 5 mm Hg. Recent surgery, which was rare in the patients in our study group, was not identified as a risk factor for PE. Conversely, the clinical symptoms supporting the suspicion of PE, such as hemoptysis, chest pain, and edema of the lower limbs, did not definitively indicate PE in our study group. We did not identify age, long-term oxygen therapy, and severity of COPD as risk factors for PE. Similarly, right-heart failure identified in 26 patients at admission was not associated with PE. Only 1 study (14) has shown that a majority of patients (23 of 26) with emphysema and PE had clinical right-heart failure on admission. Of note, this study was conducted in patients with life-threatening PE and was based on autopsy data. The present study did not include patients who required invasive mechanical ventilation or fibrinolysis, and our conclusions are therefore not valid for such populations.