The aim of our study was to evaluate the prevalence of pulmonary embolism in a selected population of patients with COPD who were admitted for severe exacerbations of unknown origin. Statistical analysis to select predictive variables for pulmonary embolism identified 3 criteria: cancer, previous thromboembolic disease, and a decrease in PaCO ₂ from baseline. It was not possible to define a specific score in patients with COPD who had a severe exacerbation of unknown origin according to a multivariate logistic regression model, as was done in the Geneva study (1). We agree that the Geneva score should not be used as the sole criterion to rule in or rule out pulmonary embolism. It should primarily be associated with a clinical probability assessment (1). In the sample we selected, alternative diagnoses, such as infection, pneumothorax, and iatrogenic event, were ruled out. In the patients with COPD who were selected according to the clinical criteria of severe exacerbation of unknown origin, we calculated the Geneva score to evaluate its diagnostic value. The prevalence of pulmonary embolism observed in patients with COPD was 9.2% (95% CI, 4.7% to 15.9%) in a low-probability group assessed by the Geneva score, similar to that observed in the Geneva study (10% [CI, 8% to 13%]) (1). A key question to consider is whether a 9% or 10% prevalence of pulmonary embolism in a low-probability group has a sufficient negative predictive value. We agree that the clinical suspicion of pulmonary embolism is particularly difficult in patients with COPD. However, missing 1 of 10 diagnoses of pulmonary embolism in the low-probability group could be deleterious in a population with poor respiratory condition at baseline.

Dr. Le Gal's and Dr. Righini's second comment concerns the modified Geneva score. We agree that this score was not prospectively evaluated and needs further validation. In our clinical practice, only 3% of patients with COPD admitted for severe exacerbation have had a recent surgical procedure. Surgery is included in the Geneva score (3 points) (1). In patients with COPD, cancer is much more prevalent (2) and was a risk factor for pulmonary embolism in our study. For this reason, we modified the Geneva score with a more relevant risk factor for patients with COPD. This score currently has no clinical value since it has not yet been validated in a prospective study.