From the authors:

From the authors:

We thank E. Marchand for his interest and comments regarding our manuscript. We agree that our cohort of severe chronic obstructive pulmonary disease (COPD) patients undergoing lung transplantation 1 differed from the original BODE (body mass index, airflow obstruction, dyspnoea and exercise capacity) index validation cohort 2 by being of a younger age and by the absence of current smokers. This may have led, as suggested, to an underestimation of our cohort's predicted survival.

However, pulmonary hypertension 3, 4 and hypercapnia 5, 6 are other COPD prognostic factors that may have differentiated our cohort from the BODE index validation cohort. Indeed, as both are longstanding criteria for lung transplant listing in COPD patients 7, it is likely that patients with hypercapnia and pulmonary hypertension were over-represented in our cohort when compared to patients with similar BODE index scores in the BODE index validation cohort. In contrast to the differences in age and current smoking status, this may have led to an overestimation of our cohort's predicted survival.

As acknowledged in our article, the BODE index has not been specifically validated in a COPD population listed for transplantation. The 95% confidence interval of predicted survival was therefore used in our analysis. We believe that this allowed to account for most of the comorbidity differences between our cohort and the BODE index validation cohort.

The Lung Allocation Score (LAS), implemented in the USA since 2005, would theoretically be a more transplantation-specific predictor of survival. However, in contrast to the BODE index, it has not been prospectively validated. The survival probability while on waiting list and 1 yr after transplantation were both used to design the LAS. As such, it cannot be used to determine the effect of lung transplantation on survival. Furthermore, although an association with the probability of dying while on a waiting list has been demonstrated 8, the LAS has not been validated as a predictor of the duration of survival. The BODE index may not be the perfect tool to predict mortality in a COPD population listed for transplantation. Nevertheless, it is probably the best currently available one.

• ©ERS 2010