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American Journal of Respiratory and Critical Care Medicine Vol 171. pp. 1317, (2005)
© 2005 American Thoracic Society

Correspondence

Dissociation of Lung Function and Airway Inflammation in Chronic Obstructive Pulmonary Disease

Is It a Real or Statistical Phenomenon?

To the Editor:

We read with interest the article by Lapperre and colleagues (1) wherein it is concluded that "airflow limitation, airway inflammation, and features commonly associated with asthma are separate and largely independent factors in the pathophysiology of COPD." This statement seems to be much too definitive, considering the limitations of the study.

First, the conclusions are based entirely on the factor analysis. The literature data (2, 3), as well as our experience with this analysis (4), indicate that results are highly dependent on the selected set of variables, the relationships between them (linear or nonlinear), and the criteria used about factor structure, and suggest that one should be very careful in their interpretation.

Second, the study is cross-sectional, not longitudinal, which, combined with the heterogeneity of multifaceted chronic obstructive pulmonary disease (COPD), and a variable natural history of the individual disease (5), might be another reason for the authors to arrive at the conclusion about the dissociation of lung function and airway inflammation.

Relationships between airway inflammation and lung function in COPD do exist, but they are not simple and easily detectable, because even the exacerbations are associated with a lower and more variable inflammatory response than those in patients with asthma (6).

These considerations do not diminish the importance of the findings of Lapperre and colleagues (1) regarding the multidimensional profile of COPD and necessity for comprehensive evaluation of the disease.

Stefan Kostianev and Blagoi Marinov

Medical University of Plovdiv, Plovdiv, Bulgaria

FOOTNOTES

Conflict of Interest Statement: None of the authors have a financial relationship with a commercial entity that has an interest in the subject of this manuscript.

REFERENCES

  1. Lapperre TS, Snoeck-Stroband JB, Gosman MME, Stolk J, Sont JK, Jansen DF, Kerstjens HAM, Postma DS, Sterk PJ, and the Glucold Study Group. Dissociation of lung function and airway inflammation in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2004; 170:499–504.[Abstract/Free Full Text]
  2. Mardia KV, Kent JT, Bibby JM. Factor analysis. In: Mardia KV, Kent JT, Bibby JM, editors. Multivariate analysis. London, UK: Academic Press; 1979. pp. 255–280.
  3. Lawlor DA, Ebrahim S, May M, Davey Smith G. (Mis)use of factor analysis in the study of insulin resistance syndrome. Am J Epidemiol 2004;159:1013–1018.[Abstract/Free Full Text]
  4. Kostianev SS, Hodzhev VA, Todorov IT, Hristova AS, Mandulova PV, Iluchev DH. A factor analysis of dyspnea indexes and lung function parameters in patients with chronic obstructive pulmonary disease. Folia Med (Plovdiv) 2001;43:27–31.
  5. Celli BR, MacNee W, and Committee Members. Standards for the diagnosis and treatment of patients with COPD: a summary of the ATS/ERS position paper. Eur Respir J 2004;23:932–946.[Free Full Text]
  6. Bhowmik A, Seemungal TAR, Sapsford RJ, Wedzicha JA. Relation of sputum inflammatory markers to symptoms and lung function changes in COPD exacerbations. Thorax 2000;55:114–120.[Abstract/Free Full Text]




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HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Proc. Am. Thorac. Soc. Am. J. Respir. Cell Mol. Biol.
Copyright © 2005 American Thoracic Society