0
Correspondence |

Response FREE TO VIEW

Jiyong Jing, MD; Tiancha Huang, MD; Wei Cui, MD; Hua-hao Shen, MD, PhD, FCCP
Author and Funding Information

Affiliations: Dr. Shen is affiliated with the Department of Respiratory Medicine, and Drs. Jing, Huang, and Cui are affiliated with the ICU in the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, People's Republic of China.

Correspondence to: Hua-hao Shen, MD, PhD, FCCP, Department of Respiratory Medicine, Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Rd, Hangzhou 310009, Zhejiang Province, People's Republic of China; e-mail: hh_shen@yahoo.com.cn


Financial/nonfinancial disclosures: The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).


© 2009 American College of Chest Physicians


Chest. 2009;136(6):1701-1702. doi:10.1378/chest.09-1767
Text Size: A A A
Published online

To the Editor:

In his letter regarding our article,1 Dr. Pereira stated that substituting forced expiratory volume in 6 s (FEV6) for FVC to determine airflow obstruction would reduce the sensitivity of spirometry findings, especially in elderly patients with mild airflow obstruction.2 This has also been noticed by other investigators.3,4

One key point to Dr. Pereira's comments is the use of a cutoff value for FEV6 to determine airflow obstruction, which is also one cause of the heterogeneity of our study. For example, since FEV6 cannot be greater than FVC, one can anticipate that the false-positive values for the FEV1/FEV6 ratio should be zero. Why did it reach 30% in the study by Gleeson et al?5 The reason for that is the lower limit of the reference values for FEV6 and FVC, both of which were obtained from the study by Hankinson et al.6 Studies from Soares et al2 and others3 have shown a low sensitivity in patients with mild airflow obstruction, because they have also used a fixed ratio for the cutoff values of FVC or FEV6.

Because the process of aging affects lung volumes, the use of this fixed ratio may result in the overdiagnosis of airflow obstruction in elderly persons, especially in those with mild disease. Therefore, the current Global Initiative for Chronic Obstructive Lung Disease guidelines7 advise that using a lower limit of normal values for FEV1/FVC ratio, which is based on a normal distribution and classifies the bottom 5% of the healthy population as abnormal, is one way to minimize the potential misclassification. If a lower limit is used for FEV6, it should be applied to FVC too. We think that no remarkable difference would be seen in the results while evaluating the FEV1/FEV6. Also, the simplicity of using FEV6 in place of FVC would be sacrificed if a lower limit for FEV6 is utilized. However, reference equations using post-bronchodilator therapy FEV1 and longitudinal studies to validate the use of the lower limit of normal are urgently needed. The only such equations currently available are those from the National Health and Nutrition Examination Study III study.

The primary significance of using the FEV1/FEV6 ratio is to reduce the misclassification rates in the multitude of settings where a volume-time plateau is rarely obtained. Many people operating spirometers have misinterpreted the traditional spirometry guidelines, which allow them to quit coaching patients after 6 s (even when the patient could have exhaled much more air), and this practice frequently causes the reported FEV1/FVC ratio to be higher than the true value. The use of the reference values for FEV1/FEV6 ratio is more appropriate in these settings, since it reduces the misclassification for detecting airway obstruction when compared with using the FEV1/FVC ratio reference values.

Jing JY, Huang TC, Cui W, et al. Should FEV1/FEV6replace FEV1/FVC ratio to detect airway obstruction? A metaanalysis. Chest. 2009;135:991-998. [PubMed] [CrossRef]
 
Soares AL, Rodrigues SC, Pereira CA. Airflow limitation in Brazilian Caucasians: FEV1/FEV6vs. FEV1/FVC. J Bras Pneumol. 2008;34:468-472. [PubMed]
 
Demir T. Response: utilization of FEV6in place of FVC may lead to the underestimation of mild airway obstruction [letter]. Respir Med. 2005;99:1617. [PubMed]
 
Crapo RO. The role of FEV6in the detection of airway obstruction [letter]. Respir Med. 2005;99:1467. [PubMed]
 
Gleeson S, Mitchell B, Pasquarella C, et al. Comparison of FEV6and FVC for detection of airway obstruction in a community hospital pulmonary function laboratory. Respir Med. 2006;100:1397-1401. [PubMed]
 
Hankinson JL, Odencrantz JR, Fedan KB. Spirometric reference values from a sample of the general US population. Am J Respir Crit Care Med. 1999;159:179-187. [PubMed]
 
Global Initiative for Chronic Obstructive Lung Disease Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease (updated 2008). 2008;Accessed October 29, 2009 Available at:http://www.goldcopd.org.
 

Figures

Tables

References

Jing JY, Huang TC, Cui W, et al. Should FEV1/FEV6replace FEV1/FVC ratio to detect airway obstruction? A metaanalysis. Chest. 2009;135:991-998. [PubMed] [CrossRef]
 
Soares AL, Rodrigues SC, Pereira CA. Airflow limitation in Brazilian Caucasians: FEV1/FEV6vs. FEV1/FVC. J Bras Pneumol. 2008;34:468-472. [PubMed]
 
Demir T. Response: utilization of FEV6in place of FVC may lead to the underestimation of mild airway obstruction [letter]. Respir Med. 2005;99:1617. [PubMed]
 
Crapo RO. The role of FEV6in the detection of airway obstruction [letter]. Respir Med. 2005;99:1467. [PubMed]
 
Gleeson S, Mitchell B, Pasquarella C, et al. Comparison of FEV6and FVC for detection of airway obstruction in a community hospital pulmonary function laboratory. Respir Med. 2006;100:1397-1401. [PubMed]
 
Hankinson JL, Odencrantz JR, Fedan KB. Spirometric reference values from a sample of the general US population. Am J Respir Crit Care Med. 1999;159:179-187. [PubMed]
 
Global Initiative for Chronic Obstructive Lung Disease Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease (updated 2008). 2008;Accessed October 29, 2009 Available at:http://www.goldcopd.org.
 
NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging & repositioning the boxes below.

  • CHEST Journal
    Print ISSN: 0012-3692
    Online ISSN: 1931-3543