In Replay:Isolated Reduction of the FEV3/FVC Ratio as an Indicator of Mild Airflow Obstruction

Abstract

Because of the concerns expressed by Dr Madan and colleagues regarding the physiologic changes that occur with aging, we analyzed the data from our article1Morris ZQ Coz A Starosta D An isolated reduction of the FEV3/FVC ratio is an indicator of mild lung injury.Chest. 2013; 144: 1117-1123Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar 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.1Morris ZQ Coz A Starosta D An isolated reduction of the FEV3/FVC ratio is an indicator of mild lung injury.Chest. 2013; 144: 1117-1123Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar 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.2Hansen 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: 349-355Abstract Full Text Full Text PDF PubMed Scopus (204) Google Scholar 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,3Pauwels 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. 2701AGoogle Scholar unfortunately has proliferated into widespread use as an all-encompassing method for interpreting spirometry for all diseases. 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 al4Hansen JE Sun X-G Wasserman K Discriminating measures and normal values for expiratory obstruction.Chest. 2006; 129: 369-377Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar clearly showed the association of smoking to a reduction in this ratio. Our study supported this relationship. In 1984, Morris et al5Morris AH Kanner RE Crapo RO Gardner RM Clinical Pulmonary Function Testing. A Manual of Uniform Laboratory Procedures. Intermountain Thoracic Society, Salt Lake City, UT1984: 21-23Google Scholar 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. Isolated Reduction of the FEV3/FVC Ratio as an Indicator of Mild Airflow ObstructionCHESTVol. 145Issue 3PreviewWe read with keen interest the recent article by Morris et al1 in CHEST (October 2013) in which they describe the use of the FEV3/FVC ratio in diagnosis of early airflow obstruction (termed as mild lung injury by the authors). However, certain important issues need to be highlighted. It is important to interpret these observations in concert with clinical and radiologic features to ascertain whether reduction in FEV3/FVC ratio translates into clinically relevant patient outcomes. Full-Text PDF