FEV6 and FEV1/FEV6 in Japanese participants of the community-based annual health check: The Takahata study

Abstract

Background Forced expiratory volume in 6 seconds (FEV6) is becoming a substitute of forced vital capacity (FVC). However, the Japanese predictive equation for FEV6 has not been established, and the validity for the use of FEV1/FEV6 for diagnosing airflow limitation in Japanese has not been confirmed. Methods Subjects aged 40 or older, who had participated in a community-based health check in Takahata, Japan, from 2004 through 2005, were enrolled. The smoking histories of these subjects were investigated using a self-reporting questionnaire. FVC, FEV1, and FEV6 were measured using spirometric machines. Predictive equations of FEV6 were obtained from never-smoking subjects without history of pulmonary diseases by multiple linear regression assay. Results FEV6 and FEV1/FEV6 were significantly correlated with FVC (r=0.998, p<0.001) and FEV1/FVC (r=0.989, p<0.001), respectively. The cutoff values of percent predicted (%) FEV6 and FEV1/FEV6 for discrimination of having the restrictive lung disorder determined by %FVC <0.8 and having the airflow limitation determined by FEV1/FVC <0.7 were 0.80 and 0.72, respectively (%FEV6: sensitivity=0.995, specificity=0.983, positive predictive value =0.832, negative predictive value =1.000; FEV1/FEV6: sensitivity=0.942; specificity=0.971; PPV=0.787; NPV=0.993). When the 5th percentile the lower limit of normal values was used as criterion for discrimination of having airflow limitation, sensitivity, specificity, PPV, and NPV of FEV1/FEV6 were 0.932, 0.985, 0.808, and 0.995, respectively. Conclusion The results of the present study suggest that %FEV6 and FEV1/FEV6 are excellent substitutes for %FVC and FEV1/FVC, respectively. We confirmed the validity of the use of FEV6 and FEV1/FEV6 for identifying pulmonary diseases in Japanese individuals. © 2011 The Japanese Society of Internal Medicine.