FEV1/FEV6 for Detection of Airflow Obstruction Response - Chest ...

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7 Cohen AT, Davidson BL, Gallus AS, et al. Efficacy and safety
of fondaparinux for the prevention of venous thromboembolism
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FEV 1/FEV 6 for Detection of Airflow
Obstruction
Better Forget It
To the Editor:
The FEV 1/forced expiratory volume in 6 s (FEV 6) ratio has
been proposed for diagnosis of airflow obstruction (AO). A recent
metaanalysis 1 concluded that FEV 1/FEV 6 ratio is a valid alternative
to the FEV 1/FVC ratio. This conclusion is questionable. In 5
of the 11 studies included in the metaanalysis, the standard for
the diagnosis of AO was an FEV 1/FVC ratio of 70%. This fixed
value decreases the sensitivity of the FEV 1/FVC ratio.
Since FEV 6 cannot be greater than FVC, one can anticipate
that the number of false-positive values for the FEV 1/FEV 6 ratio
should be zero. In one study included in the metaanalysis
(reference 28), 1 this value reached 30% of total sample.
Reduced end-expiratory flows and prolonged expiratory times,
which commonly exceed 6 s, occur in the initial stage of AO. The
FEV 1/FEV 6 ratio can therefore lose sensitivity in early diagnoses,
especially in aging patients, in whom the time required to
complete the FVC maneuver increases. 2 In two studies (references
22 and 25) included in the study by Hansen et al, 2 it was
possible to calculate the sensitivity of the FEV 1/FEV 6 ratio in
patients with mild AO. The values decreased to 73% and 82%,
respectively. In a recent study, 3 we compared the sensitivity of
FEV 1/FVC ratio and FEV 1/FEV 6 ratio in patients with mild AO.
The sensitivity for the FEV 1/FEV 6 ratio was only 75%. The
exclusion of unpublished studies can introduce bias. In one such
study (reference 10 in Soares et al 3 ), 1,926 spirometry tests were
evaluated. The sensitivity was for the FEV 1/FEV 6 ratio was
85.6%, but this value decreased to 74% among patients with mild
obstruction.
In conclusion, substituting FEV 6 for FVC to determine AO
reduces the sensitivity of spirometry findings, especially in older
individuals and in those persons with mild AO.
Carlos A. C. Pereira, PhD
São Paulo, Brazil
Affiliations: Dr. Pereira is affiliated with the Paulista School of
Medicine.
Financial/nonfinancial disclosures: The author has 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.
Correspondence to: Carlos A. C. Pereira, Paulista School of
Medicine, Av Iraí, 393, conj 34, São Paulo 04082-001, Brazil;
e-mail: pereirac@uol.com.br
© 2009 American College of Chest Physicians. Reproduction
of this article is prohibited without written permission from the
American College of Chest Physicians (www.chestjournal.org/site/
misc/reprints.xhtml).
DOI: 10.1378/chest.09-1232
References
1 Jing JY, Huang TC, Cui W, et al. Should FEV1/FEV6 replace
FEV1/FVC ratio to detect airway obstruction? A metaanalysis.
Chest 2009; 135:991–998
2 Hansen JE, Sun XG, Wasserman K. Should forced expiratory
volume in six seconds replace forced vital capacity to detect
airway obstruction? Eur Respir J 2006; 27:1244–1250
3 Soares AL, Rodrigues SC, Pereira CA. Airflow limitation in
Brazilian Caucasians: FEV1/FEV6 vs. FEV1/FVC. J Bras Pneumol
2008; 34:468–472
Response
To the Editor:
In his letter regarding our article, 1 Dr. Pereira stated that
substituting forced expiratory volume in 6 s (FEV 6) 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 FEV 6 to determine airflow obstruction, which is also
one cause of the heterogeneity of our study. For example, since
FEV 6 cannot be greater than FVC, one can anticipate that the
false-positive values for the FEV 1/FEV 6 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 FEV 6 and
FVC, both of which were obtained from the study by Hankinson
et al. 6 Studies from Soares et al 2 and others 3 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 FEV 6.
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 guidelines 7 advise that using a lower limit of
normal values for FEV 1/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 FEV 6, it should be applied
to FVC too. We think that no remarkable difference would be
seen in the results while evaluating the FEV 1/FEV 6. Also, the
simplicity of using FEV 6 in place of FVC would be sacrificed if a
lower limit for FEV 6 is utilized. However, reference equations
using post-bronchodilator therapy FEV 1 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 FEV 1/FEV 6 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 FEV 1/FVC
ratio to be higher than the true value. The use of the reference
values for FEV 1/FEV 6 ratio is more appropriate in these settings,
www.chestjournal.org CHEST / 136 /6/DECEMBER, 2009 1701
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since it reduces the misclassification for detecting airway obstruction
when compared with using the FEV 1/FVC ratio reference values.
Jiyong Jing, MD
Tiancha Huang, MD
Wei Cui, MD
Hua-hao Shen, MD, PhD, FCCP
Hangzhou, People’s Republic of China
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.
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.
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
© 2009 American College of Chest Physicians. Reproduction
of this article is prohibited without written permission from the
American College of Chest Physicians (www.chestjournal.org/site/
misc/reprints.xhtml).
DOI: 10.1378/chest.09-1767
References
1 Jing JY, Huang TC, Cui W, et al. Should FEV1/FEV6 replace
FEV1/FVC ratio to detect airway obstruction? A metaanalysis.
Chest 2009; 135:991–998
2 Soares AL, Rodrigues SC, Pereira CA. Airflow limitation in
Brazilian Caucasians: FEV1/FEV6 vs. FEV1/FVC. J Bras
Pneumol 2008; 34:468–472
3 Demir T. Response: utilization of FEV6 in place of FVC may
lead to the underestimation of mild airway obstruction
[letter]. Respir Med 2005; 99:1617
4 Crapo RO. The role of FEV6 in the detection of airway
obstruction [letter]. Respir Med 2005; 99:1467
5 Gleeson S, Mitchell B, Pasquarella C, et al. Comparison of
FEV6 and FVC for detection of airway obstruction in a
community hospital pulmonary function laboratory. Respir
Med 2006; 100:1397–1401
6 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
7 Global Initiative for Chronic Obstructive Lung Disease. Global
strategy for the diagnosis, management, and prevention of chronic
obstructive pulmonary disease (updated 2008), 2008. Available
at: http://www.goldcopd.org. Accessed October 29, 2009
Health-Care–Associated Pneumonia
Is Primarily Due to Aspiration
Pneumonia
To the Editor:
In a recent issue of CHEST (March 2009), Shindo and coworkers 1
reported the clinical features of health-care–associated pneumonia
(HCAP) and the mortality rate among patients hospitalized with HCAP
in Japan. They found that a therapeutic strategy for patients with
moderate HCAP holds the key to reducing mortality. Physicians
may need to consider potentially drug-resistant (PDR) pathogens when
selecting the initial empirical antibiotic treatment for HCAP.
We completely agree with the authors that the occurrence of
PDR pathogens is associated with an unsuccessful initial treatment
and inappropriate initial antibiotic treatment. However, the
origin of PDR pathogens and the mechanisms underlying HCAP
were not fully described in their article.
Because the average life span of individuals has rapidly increased
in developed countries, most of the hospitalized patients
with pneumonia are older patients, who are likely to aspirate
oropharyngeal contents during the night without witness. 2,3 In a
previous study, 3 we conducted a swallowing function test and
reported a very high incidence of aspiration pneumonia among
hospitalized patients with pneumonia, including communityacquired
pneumonia (CAP) and hospital-acquired pneumonia
(HAP). The criteria for the diagnosis of HCAP are consistent with
the features of aspiration pneumonia. We found that patients
with a history of hospitalization of 2 days in the preceding 90
days and a stay at a nursing home or extended care facility had a
high risk for aspiration pneumonia.
In fact, the data collected by the authors indicated that the
patients with HCAP are older than those with CAP (mean age,
81.3 years vs 69.7 years, respectively). Gram-negative pathogens
and streptococci other than Streptococcus pneumoniae, Pseudomonas
aeruginosa, and methicillin-resistant Streptococcus aureus
were isolated more frequently in HCAP patients than in CAP
patients. Silent aspiration is extremely common in the elderly
patients, and aspiration during the night is the primary cause of
pneumonia in the elderly. Oropharyngeal materials contain
Gram-negative pathogens and streptococci, which are aspirated
into the lower airways of patients with dysphagia. Hence, the
severity of pneumonia and the occurrence of PDR pathogens
were considerably affected by swallowing dysfunction rather than
the locations where pneumonia had occurred.
Aspiration pneumonia frequently recurs, and it is initially
diagnosed as CAP. However, within the next 90 days of hospitalization,
the condition should be diagnosed as HCAP. If not, it
leads to poor prognosis of HCAP and a higher number of PDR
pathogens in patients with HCAP. Hence, the initial treatment of
HCAP should be similar to that for HAP and ventilator-associated
pneumonia. 4 The Japanese guidelines for the management of
pneumonia recommend a therapeutic strategy for aspiration pneumonia
that is very similar to that for the management of
ventilator-associated pneumonia or HAP.
It is important to bear this in mind for elucidating a preventive
strategy for HCAP. Because aspiration pneumonia is predominant
in patients with HCAP, swallowing rehabilitation and oral
care may prove to be very effective in reducing the incidence of
HCAP in the future. 5,6 The evidence of the effectiveness of
therapeutic modalities for aspiration pneumonia may be applicable
for a majority of the HCAP patients.
Shinji Teramoto, MD, PhD, FCCP
Masahiro Kawashima, MD
Kosaku Komiya, MD
Shunsuke Shoji, MD, PhD
Tokyo, Japan
Affiliations: Drs. Teramoto, Kawashima, Komiya, and Shoji are
affiliated with the Department of Pulmonary Medicine, National
Hospital Organization, Tokyo National Hospital, Tokyo, Japan.
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.
Correspondence to: Shinji Teramoto, MD, Department of
Pulmonary Medicine, National Hospital Organization, Tokyo
National Hospital, 3-1-1 Takeoka Kiyose-shi, Tokyo 204-8585,
Japan; e-mail: shinjit-tky@umin.ac.jp
© 2009 American College of Chest Physicians. Reproduction
of this article is prohibited without written permission from the
American College of Chest Physicians (www.chestjournal.org/site/
misc/reprints.xhtml).
DOI: 10.1378/chest.09-1204
1702 Correspondence
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