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Is exposure to biomass smoke really associated with COPD?

Authors Das V, Nitin V, Salvi S, Kodgule R

Received 12 November 2016

Accepted for publication 28 November 2016

Published 17 February 2017 Volume 2017:12 Pages 651—653

DOI https://doi.org/10.2147/COPD.S127466

Checked for plagiarism Yes

Editor who approved publication: Dr Richard Russell


Vandana Das, Vanjare Nitin, Sundeep Salvi, Rahul Kodgule

Department of Pulmonary Function Laboratory, Chest Research Foundation, Pune, Maharashtra, India

We read the article by Balcan et al1 with great interest. The authors have reported a case–control study that included 115 females and looked at the association between exposure to biomass smoke and detection of COPD. Although the authors concluded a positive association, we are concerned about the issues related to the conduct of the study and discrepancies in the data reported. COPD cases in this study were defined based on pre-bronchodilator forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) ratio <0.70. However, the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines define COPD based on post-bronchodilator FEV1/FVC ratio <0.70. Hence, many subjects detected to have COPD in this study may actually have had asthma, in which case, the findings of the study would not apply to the COPD population. Also the overall population included in the study was relatively younger (18–48 years). Use of a fixed ratio of FEV1/FVC is likely to lead to underdiagnosis of airflow limitation in this age group.2 Use of lower limits of normal would have been a better approach. Also, COPD is more common in age groups above 40 years. Therefore, we are not convinced about the selection of population with younger age. (Open PDF to read the full Letter)

Authors’ reply
Baran Balcan1
Selcuk Akan2
Aylin Ozsancak Ugurlu1
Bahar Ozcelik Handemir3
Berrin Bagcı Ceyhan4
Sevket Ozkaya5
 
1Department of Pulmonary Medicine, Baskent University Faculty of Medicine, Istanbul, 2Department of Internal Medicine, Ankara Education and Teaching Hospital, Ankara, 3Department of Pulmonary Medicine, Irmet Hospital, Tekirdag˘, 4Department of Pulmonary Medicine, Marmara University Faculty of Medicine, 5Department of Pulmonary Medicine, Faculty of Medicine, Bahçeşehir University, Istanbul, Turkey
 
According to GOLD guidelines, post-bronchodilator pulmonary function test results are taken into account to diagnose COPD. As this is a standard criterion according to GOLD, we did not mention it in the methodology section, though we used post-bronchodilator results. Moreover, it is known that in a standard spirometry test, the best of three attempts should be taken into consideration; therefore, we did not mention that the best of three attempts was taken. (Open PDF to read full Response) 

View original paper by Balcan and colleagues.


 

Dear editor

We read the article by Balcan et al1 with great interest. The authors have reported a case–control study that included 115 females and looked at the association between exposure to biomass smoke and detection of COPD. Although the authors concluded a positive association, we are concerned about the issues related to the conduct of the study and discrepancies in the data reported. COPD cases in this study were defined based on pre-bronchodilator forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) ratio <0.70. However, the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines define COPD based on post-bronchodilator FEV1/FVC ratio <0.70. Hence, many subjects detected to have COPD in this study may actually have had asthma, in which case, the findings of the study would not apply to the COPD population. Also the overall population included in the study was relatively younger (18–48 years). Use of a fixed ratio of FEV1/FVC is likely to lead to underdiagnosis of airflow limitation in this age group.2 Use of lower limits of normal would have been a better approach. Also, COPD is more common in age groups above 40 years. Therefore, we are not convinced about the selection of population with younger age.

The case definition was based entirely on spirometry which is susceptible to errors. Interpretation from 3 acceptable and 2 repeatable graphs ensures good-quality measurements. However, the authors did not report how the quality of spirometry was ensured and how many participants performed good-quality spirometry.3 It is difficult to believe that all 100% of the study participants performed good-quality spirometry.

The authors defined small airway disease as forced expiratory flow 25%–75% (FEF25%–75%) <60% predicted. However, the values of FEF25%–75% are also reduced in subjects with lower FVC. Hence, use of the ratio of FEF25%–75% to FVC corrects for the effect of reduced FVC and provides more reliable information.4 Considering 20 cases with reduced FVC suggests significant confounding of the association with small airways disease due to reduced FVC.

We would also like to highlight the issues related to the statistical tests used and data reported. The authors have reported lung function data in median and inter-quartile range. The visual impression of Figure 3 suggests that the data were not normally distributed. However, the authors have compared the two groups (cases and controls) using the parametric t-test. A non-parametric test in this instance would have been more appropriate. The numbers reported in different tables did not match with each other. For example, the authors report 27 participants as having small airways disease in Table 3, whereas they report 17 participants as having small airways disease in Table 5. Also in Table 5 the authors have reported that 115 participants (95 without restriction and 20 with restriction) had FEV1/FVC >70% suggesting that no one had reduced ratio, which emphasizes that no one in the study group had COPD.

In view of the above limitations, we wish to alert the readers of the journal to interpret the results of this study cautiously.

Disclosure

The authors report no conflicts of interest in this communication.


References

1.

Balcan B, Akan S, Ugurlu AO, Handemir BO, Ceyhan BB, Ozkaya S. Effects of biomass smoke on pulmonary functions: a case control study. Int J Chron Obstruct Pulmon Dis. 2016;11:1615–1622.

2.

Cerveri I, Corsico AG, Accordini S, et al. What defines airflow obstruction in asthma? Eur Respir J. 2009;34(3):568–573.

3.

Miller MR, Hankinson J, Brusasco V, et al; ATS/ERS Task Force. Standardisation of spirometry. Eur Respir J. 2005;26(2):319–338.

4.

Litonjua AA, Sparrow D, Weiss ST. The FEF25-75/FVC ratio is associated with methacholine airway responsiveness. The normative aging study. Am J Respir Crit Care Med. 1999;159(5 Pt 1):1574–1579.

Authors’ reply

Baran Balcan,1 Selcuk Akan,2 Aylin Ozsancak Ugurlu,1 Bahar Ozcelik Handemir,3 Berrin Bagci Ceyhan,4 Sevket Ozkaya5

1Department of Pulmonary Medicine, Baskent University Faculty of Medicine, Istanbul, 2Department of Internal Medicine, Ankara Education and Teaching Hospital, Ankara, 3Department of Pulmonary Medicine, Irmet Hospital, Tekirdağ, 4Department of Pulmonary Medicine, Marmara University Faculty of Medicine, 5Department of Pulmonary Medicine, Faculty of Medicine, Bahçeşehir University, Istanbul, Turkey

Correspondence: Baran Balcan, Department of Pulmonary Medicine, Baskent University Faculty of Medicine, 7 Oymaci Street, Istanbul 34662, Turkey, Tel +90 530 414 2308, Fax +90 216 554 1500, Email drbaranbalcan@yahoo.com

Dear editor

According to GOLD guidelines, post-bronchodilator pulmonary function test results are taken into account to diagnose COPD. As this is a standard criterion according to GOLD, we did not mention it in the methodology section, though we used post-bronchodilator results. Moreover, it is known that in a standard spirometry test, the best of three attempts should be taken into consideration; therefore, we did not mention that the best of three attempts was taken.

In addition we excluded allergic diseases such as asthma based on both the spirometry results and the past medical history of patients (patients who were diagnosed with asthma and allergic rhinitis were also excluded).

This study was performed in a territory that has poor environmental setting and technical supports. We evaluated the patients using simple pulmonary function tests. Advanced tests such as radiological imaging with chest X-ray or computed tomography should have been performed to attain accuracy, but we were lacking these types of supports.

Disclosure

The authors report no conflicts of interest in this communication.

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