Diagnostic Performance of Forced Expiratory Volume in Six Seconds for the Detection of Obstructive and Restrictive Pulmonary Diseases in a Population of Young Adults in South of Iran

Background: Forced expiratory volume in ۶ seconds (FEV۶) is a reliable substitute for forced vital capacity (FVC) to identify pulmonary diseases. This study aimed to determine the diagnostic performance of FEV۶ in the detection of obstructive and restrictive spirometric patterns. Methods: In this cross-sectional study, spirometry was performed on patients referred to the occupational medicine clinic of Shahid Mohammadi Hospital, Bandar Abbas, Iran, ۲۰۱۸. Spirometric parameters, including FEV۱, FVC, and FEV۶, were recorded for those tests meeting the American Thoracic Society (ATS) standards. Taken as the reference, the FEV۱/FVC ratio < ۷۰% indicated airway obstruction, and the restrictive pattern was defined as FVC < ۸۰%. Results: In general, ۱۱۰۰ spirometries were included after meeting the ATS standards. The optimal cut-off of FEV۱/FEV۶ for the prediction of airway obstruction was ۷۱.۴۵% with a sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of ۹۷.۲۲%, ۹۸.۲۲%, ۸۹.۱۷%, ۹۹.۵۷%, and ۹۸.۰۹%, respectively. The best cut-off of FEV۶ for the prediction of the restrictive pattern was ۷۹.۲۳% with the corresponding diagnostic indices of ۹۷.۲۹%, ۹۹.۰۵%, ۹۴.۱۱%, ۹۹.۵۷%, and ۹۸.۸۱%, respectively. Based on the FEV۱/FEV۶ cut-off, the frequency of obstruction was ۱۴.۲۷% (۱۵۷/۱۱۰۰) compared to ۱۳.۰۹% based on FEV۱/FVC. The frequency of restriction was ۱۳.۹۰% (۱۵۳/۱۱۰۰) according to the FEV۶ cut-off compared to ۱۳.۴۵% with respect to FVC. Conclusion: Overall, our results indicated the applicability of FEV۱/FEV۶ as an accepted surrogate for FEV۱/FVC to diagnose airway obstruction, particularly to screen for chronic obstructive pulmonary disease (COPD) among high-risk patients. In addition, FEV۶ is potentially an appropriate substitute for FVC to detect a restrictive pattern.

Keywords:

Forced expiratory volume , Sensitivity and specificity , Airway obstruction , Airway restriction