From the authors:
We greatly appreciate the letter from M. González-García and C. Torres-Duque in response to our paper comparing the different phenotypes of chronic obstructive pulmonary disease (COPD) in tobacco smoke- versus biomass smoke-induced COPD [1]. The information they provide from publications that we failed to cite strengthens the case for our conclusions and contributes to a better understanding of COPD sub-phenotypes.
A phenotype, according to Agusti [2], is the end result of the interaction between the genotype, the environment, and some degree of random variation that facilitates and/or limits these gene–environment interactions. The aim of phenotyping is to identify homogeneous groups of patients who have a different clinical course or who respond to specific therapeutic interventions. In COPD, this is an established strategy used to better understand subjects with the disease; the “pink puffer” and the “blue bloater” were the best known early phenotypes. Agusti [2] suggests that a clinical phenotype should predict at least one clinically relevant outcome that indicates that this would require longitudinal monitoring.
Our findings suggest that COPD associated with biomass exposure is a clinical phenotype with clear differences to COPD associated with tobacco smoking [[1, 3]. The very interesting comments by M. González-García and C. Torres-Duque complement the hypothesis that COPD associated with biomass exposure is a phenotype related to airways' obstruction rather than to emphysema. However, despite the considerable cross-sectional evidence [[4–7] that biomass smoke causes a different expression of COPD, there is a paucity of data on the clinical implications of this difference; for instance, is this phenotype related to a greater or lower mortality, or an accelerated or slower decline in forced expiratory volume in 1 s? As usual, much work remains to be done to discover the importance of these now well-established phenotypic differences.
Footnotes
Conflict of interest: Disclosures can be found alongside the online version of this article at www.erj.ersjournals.com
- Received February 12, 2014.
- Accepted February 18, 2014.
- © ERS 2014