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Comparative Study
. 2014 May;69(5):409-14.
doi: 10.1136/thoraxjnl-2012-202810. Epub 2013 Mar 23.

Comparison of spirometric thresholds in diagnosing smoking-related airflow obstruction

Surya P Bhatt  1 , Jessica C Sieren, Mark T Dransfield, George R Washko, John D Newell Jr, Douglas S Stinson, Gideon K D Zamba, Eric A Hoffman; COPDGene Investigators
Affiliations
Comparative Study

Comparison of spirometric thresholds in diagnosing smoking-related airflow obstruction

Surya P Bhatt et al. Thorax. 2014 May.

Abstract

Background: Diagnosis of chronic obstructive pulmonary disease is based on detection of airflow obstruction on spirometry. There is no consensus regarding using a fixed threshold to define airflow obstruction versus using the lower limit of normal (LLN) adjusted for age. We compared the accuracy and discrimination of the Global Initiative for Chronic Obstructive Lung Disease (GOLD) recommended fixed ratio of forced expiratory volume in the first second/forced vital capacity<0.70 with LLN in diagnosing smoking-related airflow obstruction using CT-defined emphysema and gas trapping as the disease gold standard.

Methods: Data from a large multicentre study (COPDGene), which included current and former smokers (age range 45-80 years) with and without airflow obstruction, were analysed. Concordance between spirometric thresholds was measured. The accuracy of the thresholds in diagnosing emphysema and gas trapping was assessed using quantitative CT as gold standard.

Results: 7743 subjects were included. There was very good agreement between the two spirometric cutoffs (κ=0.85; 95% CI 0.83 to 0.86, p<0.001). 7.3% were discordant. Subjects with airflow obstruction by fixed ratio only had a greater degree of emphysema (4.1% versus 1.2%, p<0.001) and gas trapping (19.8% vs 7.5%, p<0.001) than those positive by LLN only, and also smoking controls without airflow obstruction (4.1% vs 1.9% and 19.8% vs 10.9%, respectively, p<0.001). On follow-up, the fixed ratio only group had more exacerbations than smoking controls.

Conclusions: Compared with the fixed ratio, the use of LLN fails to identify a number of patients with significant pulmonary pathology and respiratory morbidity.

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Conflict of interest statement

Conflict of Interest Statement

MTD received consultancy fees from Boehringer Ingelheim and GlaxoSmithKline. JDN received consultancy fees from VIDA Diagnostics. EAH is the founder of and owns stocks in VIDA Diagnostics. None of the other authors has any conflicts of interest to declare, pertinent to the subject of this manuscript.

Figures

Figure 1
Figure 1
shows a scatter plot demonstrating that while there is good correlation between FEV1/FVC and measures of emphysema and gas trapping, there is considerable discordance between spirometry and CT measures for a large number of subjects. LAA = Low attenuation areas.
See this image and copyright information in PMC

Comment in

References

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