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Impact of diagnostic criteria on the prevalence of COPD

Authors

  • Yunus Çolak,

    Corresponding author
    • The Copenhagen City Heart Study, Bispebjerg Hospital, Copenhagen, Denmark
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  • Anders Løkke,

    Corresponding author
    1. Department of Respiratory Medicine, Aarhus County Hospital, Aarhus, Denmark
    • The Copenhagen City Heart Study, Bispebjerg Hospital, Copenhagen, Denmark
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  • Jacob Louis Marott,

    1. The Copenhagen City Heart Study, Bispebjerg Hospital, Copenhagen, Denmark
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  • Peter Lange,

    1. Respiratory Section, Hvidovre Hospital, Copenhagen, Denmark
    2. Department of Public Health, University of Copenhagen, Copenhagen, Denmark
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  • Jørgen Vestbo

    1. Respiratory Section, Hvidovre Hospital, Copenhagen, Denmark
    2. Respiratory Research Group, Manchester Academic Health Sciences Centre, University of Manchester, South Manchester University Hospital Trust, Wythenshawe Hospital, Manchester, UK
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  • Authorship and contributorship

    YÇ participated in the design and running of the study, discussed findings and analyses, and wrote the draft manuscript. AL participated in the design and running of the study, discussed findings and analyses, and helped in writing the draft. JLM participated in the design and running of the study, was responsible for all statistical analyses, and commented on the manuscript. PL participated in the design and running of the study, discussed findings and analyses, and commented on the manuscript. JV participated in the design and running of the study, discussed findings and analyses, helped in writing the draft as well as commented on the final version.

  • Ethics

    The study has been approved by local ethics committee and informed consent was obtained from all participants.

  • Conflict of interest

    The authors have stated explicitly that there are no conflicts of interest in connection with this article.

Correspondence

Yunus Çolak, Medical Student, The Copenhagen City Heart Study, Bispebjerg Hospital, Bispebjerg Bakke 23, 2400 Copenhagen NV, Denmark.

Tel: +45 2673 7863

Fax: +45 3531 6070

email: yunuscol@gmail.com

Anders Løkke, MD, Department of Respiratory Medicine, Aarhus County Hospital, Nørrebrogade 44, 8000 Aarhus C, Denmark.

Tel: +45 2889 4197

Fax: +45 3531 6070

email: aloekke@gmail.com

Abstract

Introduction

The reduction in the ratio between forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) is used for the diagnosis of chronic obstructive pulmonary disease (COPD). The choice between a simple fixed cut-off ratio (FEV1/FVC <0.70) and the use of lower limit of normal (LLN) is eagerly discussed. The aim of this paper was to examine the impact of these two diagnostic measures on the prevalence of COPD using data from the fourth examination of The Copenhagen City Heart Study (CCHS4).

Materials and Methodology

A total of 6237 subjects participated in CCHS4 from 2001 to 2003. Asymptomatic, healthy never-smokers of all ages with adequate information from questionnaires and spirometry were used to calculate LLN.

Results

LLN was declining with increasing age and height. If LLN was used as the correct diagnostic criterion, under- and over-diagnosis among men were 0.4% and 7.0%, respectively, and for women 2.0% and 1.4%, respectively, when using the fixed ratio. Over-diagnosis among men was reduced from 7.0% to 3.0% by changing the fixed cut-off ratio to FEV1/FVC <0.65 for subjects older than 65 years. Among women, however, this adjustment led to an increase in under-diagnosis from 2.0% to 5.7%. Most participants with FEV1/FVC <0.70 but >LLN had well-preserved FEV1.

Conclusion

Using the fixed ratio for diagnosing COPD in an epidemiological setting results in a higher prevalence than if the LLN is used. Time seems ripe for studying if the same is seen when diagnosing COPD in the clinical setting.

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