Incidence of venous thromboembolism in COPD: linking inflammation and thrombosis?

Chronic obstructive pulmonary disease (COPD) is a major health burden and expected to become the third leading cause of death by 2030 [1, 2]. Acute exacerbations with aggravation of respiratory symptoms are associated with an acceleration of progressive lung function decline and significant worsening of prognosis (in-hospital mortality rate, 10%; 3-year mortality rate, 49%) [2]. Management of patients with COPD presenting with worsening dyspnoea remains challenging and, in approximately one-third of cases, the underlying cause cannot be identified [2]. Importantly, evidence is accumulating that, in a relevant proportion of patients presenting with symptoms of an exacerbation of COPD, the underlying condition is an acute episode of pulmonary embolism. Of all the studies published over the past 10 years, which investigated the prevalence of pulmonary embolism in patients hospitalised for exacerbation of COPD [3–12] (table 1), those with a prospective study design including a standardised protocol for pulmonary embolism examination (highlighted in bold in table 1 [3, 5–7, 9–11] reported a high prevalence of pulmonary embolism (14.4% (203 of 1406 patients); range 3.3–29.1%). On the other hand, retrospective population data from 58392000 patients hospitalised with COPD from 1979 to 2003 registered in the United States National Hospital Discharge Survey suggest that, in patients with COPD, both deep vein thrombosis (632000 patients (1.08%)) and pulmonary embolism (381000 patients (0.65%)) are generally underdiagnosed in clinical practice [13]. Furthermore, in a retrospective observational study including 436 consecutive patients with acute pulmonary embolism, COPD was identified as an independent predictor of a delayed diagnosis [14]. Given the therapeutic and prognostic implications of a (missed) diagnosis of acute pulmonary embolism, it appears crucial to increase awareness of this clinical condition [15], identify predictors of pulmonary embolism in patients with COPD exacerbation [11] and incorporate pulmonary embolism into the differential diagnosis work-up of COPD patients presenting with worsening dyspnoea.