From the Editor:
I appreciate D. Lee's comments regarding my editorial on the usage of postbronchodilator spirometry in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) and American Thoracic Society/European Respiratory Society criteria for the definition and classification of patients with chronic obstructive pulmonary disease (COPD)1. Will it be meaningful to add prebronchodilator values and reversibility to those criteria? It sounds plausible, but I believe it is not justified. The reason for this is that we should distinguish the criteria for the disease from potentially relevant information on the disease.
我们似乎都同意在whi COPD是一种疾病ch airflow limitation is not fully reversible. The latter points to residual airflow limitation after giving an adequate dose of abronchodilator: in other words, a lowered ceiling (postbronchodilator value) of spirometry. Would it be helpful to include the reversibility as such? Apart from the different ways of expressing reversibility2, it appears that the response to a bronchodilator has hardly any diagnostic value for COPD3, whilst being very poorly reproducible4. As indicated in my editorial, this is not unexpected since the prebronchodilator value of forced expiratory volume in one second and, thereby, its reversibility towards the postbronchodilator ceiling value is modulated by variable degrees of smooth muscle contraction. Therefore, the prebronchodilator value, as well as the reversibility, does not seem to be an adequate criterion as to whether airflow limitation is “not fully reversible”.
Does this mean that reversibility is a useless index? No, certainly not. The degree of reversibility may point towards clinically and pathophysiologically relevant phenotypes ofCOPD. What are the determinants of smooth muscle contraction in this disease? We don't know, but there is recent evidence that patients with a substantial degree of reversibility of their airflow limitation (notwithstanding their abnormal postbronchodilator value) do have certain specific characteristics, such as elevated levels of exhaled nitric oxide and sputum eosinophilia5, together with blood eosinophilia and reduced levels of neutrophil activation6. Hence, indeed, there is a message that needs to be taken seriously in measuring reversibility, despite its poor reproducibility4.
Taken together, when distinguishing the strict criteria for the definition and classification of chronic obstructive pulmonary disease from other potentially useful information on the clinical phenotype of the disease, D. Lee and myself do seem to agree. I thank him for his comments.
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