Objective To determine the efficacy of forced expiratory volume in six seconds( FEV6 ) as an alternative for forced vital capacity( FVC) in the diagnosis for mild-moderate chronic obstructive pulmonary disease( COPD) .Methods A total of 402 mild-moderate COPD and 217 non-COPD patients’ spirometric examinations were retrospectively analyzed. The correlation between FEV6 and FVC, FEV1 /FVC and FEV1 /FEV6 was evaluated by the Spearman test. Considering FEV1 /FVC lt;70% as being the ‘golden standard’ for airway obstruction, a ROC curve was used to determine the best cut-off point for the FEV1 /FEV6 ratio in the diagnosis for COPD. Results The Spearman correlation test revealed the FEV1 and FEV6 , FEV1 /FEV6 and FEV1 /FVC ratios were highly correlated ( r = 0. 992, 0. 980, respectively, P = 0. 000) . Using FEV1 /FEV6 lt; 70% as the diagnosis standard, 12. 69% of the 402 patients could not be diagnosed as COPD. The FEV1 /FVC ratio of these patients was very close to 70% . The best cut-off point for the FEV1 /FEV6 ratio in the diagnosis of mild-moderate COPD was 72% while the sensitivity and specificity were 94. 7% and 92. 2% , respectively. Conclusions There is a b correlation between FEV1 /FVC and FEV1 /FEV6 . The FEV6 can be a valid alternative for FVC in the diagnosis for mild-moderate COPD, although it may result in false negative. The best cut-off point for the FEV1 /FEV6 ratio is 72% .
0bjective To evaluate the efficacy of FEV6 and FEV1／FEV6 as surrogates for FVC and FEV1／FVC in the spirometric diagnosis of airway obstruction，and to determine the fixed cut-off point of FEV1／FEV6 which can be used as an alternative for FEV1／FVC lt; 70％.Methods Spirometry measurements were perform ed in 128 participants．FEV1，FEV6，FVC，FEV1％pred，FVC％pred，FEV1／FVC and FEV1／FEV6 were measured and analyzed.FEV1／FVClt;70％ was used as the“gold standard”。Severity of obstruction was based on FEV ％ pred．From ROC curve analysis，the FEV1／FEV6 ratio，which corresponded to optimal combination of sensitivity and specificity，was determined．Correlation between FEV1／FVC and FEV1／FEV6 was studied．Results Of 128 participants，there were 65(51％)with FEV1／FVC ≥70％ ．Of the 63 participants with FEV1／FVC lt;70％ ，there were 5 with FEV1／FEV6 between 70.09％ to 71％。There was no significant difference between the mean value of FVC and that of FEV ．Lifear correlation was revealed between FEV1／FVC and FEV1／FEV6 with the value close to 1(r=0.9979，Plt;0.0001)．From ROC curve analysis，the FEV1／FEV6lt;71.14％ was the best cut-off point coresponding to FEV1／FVC lt;70％ ．Conclusion These results suggest that FEV1／FEV6 is a valid alternative to FEV1／FVC for spirometric diagnosis of airw ay obstruction．There is a b corelation between FEV1／FEV6 and FEV1／FVC．