Key Point:

The predominance of eosinophils or neutrophils in COPD patients may help predict the course of the disease and guide treatment decisions.

TAIPEI, TAIWAN—Eosinophils are the inflammatory cells that most often occur in patients with asthma, and neutrophils are usually found in those with COPD. However, eosinophils have also been found in some COPD patients with stable disease. Research has suggested that in COPD patients with eosinophilic airway inflammation, inhaled corticosteroids can relieve symptoms and may even influence the clinical course of the disease.

Because both the extent of bronchial reversibility and the pattern of airway inflammation influence treatment decisions in COPD, a group of Taiwanese researchers surveyed the characteristics of airway inflammation in patients with stable COPD.¹

TYPE OF INFLAMMATION AND REVERSIBILITY

The study included 88 men with COPD who were treated regularly with theophylline, oral β₂-agonists, anticholinergic drugs, and mucolytic agents. Patients had not received corticosteroids during the previous three months and had no history of rhinitis, eczema, or asthma. Pulmonary function tests were performed in the morning, followed by sputum induction testing. Also included in the study was a control group of healthy patients.

Bronchodilator reversibility was determined for all patients. Reversibility was defined as an increase in FEV₁ of more than 12% or in FVC of 200 mL 30 minutes after inhalation of 400 μg of albuterol. Sputum samples were collected after bronchodilator treatment and tested for levels of interleukin (IL)-8, normal T cells, and eotaxin.

Forty-eight patients had bronchodilator reversibility. Of these, 31 had sputum eosinophilia, as did 19 of 40 patients without bronchodilator reversibility. The percentage of neutrophils was similar in both reversible and nonreversible groups, but levels of albumin and IL-8 were significantly higher in the nonreversible group.

In all patients, the presence of neutrophils was inversely correlated with prebronchodilator and postbronchodilator FEV₁, with the strongest correlation in patients without bronchodilator reversibility. IL-8 was positively correlated with sputum levels of neutrophils and albumin but was not related to prebronchodilator and postbronchodilator FEV₁.

A significant degree of eosinophilic inflammation existed in the study population—even though no patients had a history of asthma or allergy, and all had been diagnosed using the Global Initiative for Chronic Obstructive Lung Disease guidelines. Thus, the authors noted, using sputum induction to identify characteristics of airway inflammation may prove valuable in guiding therapy and predicting clinical outcomes.

Although there was heterogeneity among the types of inflammatory cells found, eosinophils and neutrophils predominated. Inhaled corticosteroids do not affect the number of neutrophils in COPD or in asthma patients with neutrophilic airway inflammation. However, inhaled corticosteroids reduce the number of eosinophils and improve clinical symptoms in those with predominantly eosinophilic disease.

From a therapeutic standpoint, it is crucial to identify eosinophil levels in patients with COPD. At the same time, it appears that neutrophilic inflammation plays a part in nonreversible airway obstruction.

How are eosinophils recruited into the airways of COPD patients? Perhaps, the authors speculated, some of these patients also have asthma. Another possibility is that asthma patients develop COPD because of long-term exposure to cigarette smoke, which may actually constitute a large part of the overlap between asthma and COPD.

One classic feature of COPD is the lack of short-term response to bronchodilators. However, many COPD patients respond to bronchodilators in a manner similar to that in patients with asthma. In addition, a study by Tashkin and Kesten² found that COPD patients treated with bronchodilators have a better clinical outcome after one year of therapy, regardless of their short-term bronchodilator response.

—Gale Jurasek

References
1. Perng DW, Huang HY, Chen HM, et al. Characteristics of airway inflammation and bronchodilator reversibility in COPD: a potential guide to treatment. Chest. 2004;126:375-381.
2. Tashkin D, Kesten S. Long-term treatment benefits with tiotropium in COPD patients with and without short-term bronchodilator responses. Chest. 2003;123: 1325-1327.

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