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Zachary Q. Morris, MD
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From the Division of Pulmonary and Critical Care Medicine, Henry Ford Hospital.

Correspondence to: Zachary Q. Morris, MD, Division of Pulmonary and Critical Care Medicine, Henry Ford Hospital, 2799 W Grand Blvd, Detroit, MI 48202; e-mail: zmorris1@hfhs.org


Financial/nonfinancial disclosures: The author has reported to CHEST that no potential 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. See online for more details.


Chest. 2014;145(3):662-663. doi:10.1378/chest.13-2550
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To the Editor:

Because of the concerns expressed by Dr Madan and colleagues regarding the physiologic changes that occur with aging, we analyzed the data from our article1 using % predicted values (residual volume, total lung capacity, residual volume/total lung capacity, diffusing capacity of lung for carbon monoxide, and so forth) rather than absolute values and calculated the predicted values using regression equations adjusted for age, as well as sex, height, and race. This eliminated the biases introduced by the small differences in age when comparing groups.1

Dr Madan and colleagues bring up an important issue when referencing studies that demonstrate that the burden of COPD is overestimated using the FEV1/FVC ratio. This occurs as a consequence of using a fixed cutoff in all ages to define the lower limit of normal and is well recognized as problematic.2 The GOLD (Global Initiative for Chronic Obstructive Lung Disease) updates continue to promote defining a fixed lower limit of normal of 70% despite decades of research and guidelines that recommend that when interpreting pulmonary function tests one should use regression equations that adjust for age, sex, height, and race, along with their 95% confidence limits of normal. Using the latter methodology recommended by the American Thoracic Society and European Respiratory Society guidelines, we avoided this overestimation, as illustrated in Figure 1. The original GOLD document’s expert opinion of using a fixed ratio to diagnose COPD, intended as a tool for classifying and managing COPD,3 unfortunately has proliferated into widespread use as an all-encompassing method for interpreting spirometry for all diseases.

Figure Jump LinkFigure 1. NHANES predicted FEV1/FVC and lower 95% CI limit for white men. Gray regions are subjects misclassified by GOLD criteria. Just past 40 years old (vertical dotted line), as age increases, the greater the risk of overdiagnosing COPD. Under 40 years of age, GOLD calls subjects normal that are below the lower 95% confidence limit of normal. ci = confidence interval; GOLD = Global Initiative for Chronic Obstructive Lung Disease; NHANES = National Health and Nutrition Examination Survey.Grahic Jump Location

Dr Madan and colleagues also recommended that before adopting the FEV3/FVC ratio for common use, it should be validated using other radiographic and clinical assessments. But what if this is the more sensitive measurement? Without concomitant emphysema, a CT scan would appear normal unless air trapping was sufficient to cause a mosaic pattern. Clinically, subjects with milder forms of diseases such as diabetes or hypertension can remain asymptomatic for years. Hansen et al4 clearly showed the association of smoking to a reduction in this ratio. Our study supported this relationship. In 1984, Morris et al5 and the Intermountain Thoracic Society advocated using this ratio and its lower limit of normal to identify mild/midflow obstruction. Short of pathologic correlation with lung biopsies, large patient databases may be the most sensitive way to identify small physiologic differences between groups. We are not advocating that the FEV3/FVC replace the FEV1/FVC ratio, but rather feel it may have an important complimentary role in identifying milder disease. In response to the opinion that the term lung injury should be restricted to the diagnosis of ARDS, we used these words in the same context as our pathology colleagues who routinely use this phrase to describe damage to the lungs no matter what the cause, including ARDS.

References

Morris ZQ, Coz A, Starosta D. An isolated reduction of the FEV3/FVC ratio is an indicator of mild lung injury. Chest. 2013;144(4):1117-1123. [CrossRef] [PubMed]
 
Hansen JE, Sun X-G, Wasserman K. Spirometric criteria for airway obstruction: use percentage of FEV1/FVC ratio below the fifth percentile, not < 70%. Chest. 2007;131(2):349-355. [CrossRef] [PubMed]
 
Pauwels R, Anthonisen N, Bailey W, et al.Global Initiative for Chronic Obstruction Lung Disease: Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease NHLBI/WHO Workshop Report Executive Summary. Bethesda, MD: National Institutes of Health; 2001. NIH Publication No. 2701A.
 
Hansen JE, Sun X-G, Wasserman K. Discriminating measures and normal values for expiratory obstruction. Chest. 2006;129(2):369-377. [CrossRef] [PubMed]
 
Morris AH, Kanner RE, Crapo RO, Gardner RM. Clinical Pulmonary Function Testing. A Manual of Uniform Laboratory Procedures.2nd ed. Salt Lake City, UT: Intermountain Thoracic Society; 1984:21-23.
 

Figures

Figure Jump LinkFigure 1. NHANES predicted FEV1/FVC and lower 95% CI limit for white men. Gray regions are subjects misclassified by GOLD criteria. Just past 40 years old (vertical dotted line), as age increases, the greater the risk of overdiagnosing COPD. Under 40 years of age, GOLD calls subjects normal that are below the lower 95% confidence limit of normal. ci = confidence interval; GOLD = Global Initiative for Chronic Obstructive Lung Disease; NHANES = National Health and Nutrition Examination Survey.Grahic Jump Location

Tables

References

Morris ZQ, Coz A, Starosta D. An isolated reduction of the FEV3/FVC ratio is an indicator of mild lung injury. Chest. 2013;144(4):1117-1123. [CrossRef] [PubMed]
 
Hansen JE, Sun X-G, Wasserman K. Spirometric criteria for airway obstruction: use percentage of FEV1/FVC ratio below the fifth percentile, not < 70%. Chest. 2007;131(2):349-355. [CrossRef] [PubMed]
 
Pauwels R, Anthonisen N, Bailey W, et al.Global Initiative for Chronic Obstruction Lung Disease: Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease NHLBI/WHO Workshop Report Executive Summary. Bethesda, MD: National Institutes of Health; 2001. NIH Publication No. 2701A.
 
Hansen JE, Sun X-G, Wasserman K. Discriminating measures and normal values for expiratory obstruction. Chest. 2006;129(2):369-377. [CrossRef] [PubMed]
 
Morris AH, Kanner RE, Crapo RO, Gardner RM. Clinical Pulmonary Function Testing. A Manual of Uniform Laboratory Procedures.2nd ed. Salt Lake City, UT: Intermountain Thoracic Society; 1984:21-23.
 
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