Diagnosis of chronic obstructive pulmonary disease earlier than current Global Initiative for Obstructive Lung Disease guidelines using a feasible spirometry parameter (maximal-mid expiratory flow/forced vital capacity)

Abstract

Some patients suffer from clinical symptoms of chronic obstructive pulmonary disease (COPD) but their pulmonary function tests are in the normal range (at risk group). The objective of this study was to discover a practical test to distinguish these patients from non-COPD subjects. A total of 77 subjects including 40 COPD patients, 37 subjects at risk for developing COPD, and 32 control subjects were entered in this study. The accuracy of maximal-mid expiratory flow (MMEF)/forced vital capacity (FVC) for the diagnosis of COPD in at risk patients and its capability to differentiate from early COPD and normal patients were evaluated. Body plethysmography was used for measurement of lung volume as the Global Initiative for Obstructive Lung Disease standard. MMEF/FVC in the at risk group of COPD (0.73±0.19) was significantly lower than the normal control group (0.9±0.24, respectively), and also, it was significantly higher than the COPD group (0.31±0.17). There was significant correlation between the MMEF/FVC and amount of smoking measured by pack year (r2=0.112, p=0.005) and stages of COPD (Spearman's ρ=0.82, p=0.0001). Early stage COPD (smoker subjects without spirometry derangement) can be diagnosed by MMEF/FVC. Using this tool we may be able to detect this highly preventable disease at an earlier stage.