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Safety of Sputum Induction During Exacerbations of COPD^*

^* From the Department of Pulmonology (Drs. Bathoorn, Liesker, Postma, Koëter, and Kerstjens) and Laboratory of Allergology and Pulmonary Diseases (Dr. van Oosterhout), Groningen Research Institute for Asthma and COPD, University Medical Center Groningen, University of Groningen, the Netherlands.

Correspondence to: Huib A. M. Kerstjens, MD, PhD, Department of Pulmonology, University Medical Center Groningen, Postbox 30001, 9700RB, Groningen, the Netherlands; e-mail: h.a.m.kerstjens{at}int.umcg.nl

Abstract

Sputum induction (SI) is considered to be a safe tool for assessing airway inflammation in stable patients with COPD, but little is known about its safety during exacerbations. We therefore assessed the safety of SI during COPD exacerbations. SI data from 44 COPD patients were assessed both in the stable phase and during exacerbation. The median FEV₁ for the stable phase and exacerbation were 61% predicted (interquartile range [IQR], 49 to 74% predicted) and 51% predicted (IQR, 45 to 60% predicted), respectively. The median decrease in FEV₁ with SI during an exacerbation was 0.27 L (IQR, 0.17 to 0.40 L) vs 0.28 L (IQR, 0.22 to 0.44 L) during the stable phase (p = 0.03). The patients experienced the associated dyspnea well; no other adverse events occurred. All FEV₁ values returned to within 90% of their initial value within 30 min. A larger decrease in FEV₁ due to SI during an exacerbation was associated with the following parameters in the stable phase of disease: lower total sputum cell count (r = –0.37; p = 0.01); higher percentage of eosinophils (r = 0.33; p = 0.04); and a larger decrease in FEV₁ after SI (r = 0.39; p = 0.03). In a multivariate analysis, the only independent association was with the larger decrease in FEV₁ in the stable phase. We concluded that SI can be safely carried out in patients with mild-to-moderate COPD who experience an exacerbation, and this occurs with no greater risk than in stable patients with COPD.

Key Words: COPD • exacerbation • safety • sputum induction