Background/aims: Postbronchodilator forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) less than 0.7 using spirometry is the golden standard to diagnose airf low limitation of chronic obstructive pulmonary disease (COPD). Recently, measuring FEV6 has been suggested as an alternative to measure FVC. Studies about the cut-off value for FEV1/FEV6 to diagnose airflow limitation have shown variable results, with values between 0.7 and 0.8. The purpose of this study was to determine the best cut-off value of FEV1/FEV6 to detect airflow limitation using handheld spirometry.
Methods: We recruited subjects over 40 years of age with smoking history over 10 pack-years. Participants underwent measurements with both handheld spirometry and conventional spirometry. We calculated the sensitivity and specificity of the value of FEV1/FEV6 using receiver-operating characteristic (ROC) curve analysis to obtain the diagnostic accuracy of handheld spirometry to detect airflow limitation.
Results: A total of 290 subjects were enrolled. Their mean age and smoking amount were 63.1 years and 31.6 pack-years, respectively. According to our ROC curve analysis, when FEV1/FEV6 ratio was 73%, sensitivity and specificity were the maximum and the area under the ROC curve was 0.93, showing an excellent diagnostic accuracy. Sensitivity, specificity, positive predictive value, and negative predictive value were 86.7%, 89.7%, 88.0%, and 88.5%, respectively. Participants with FEV1/FEV6 ≤ 73% had lower FEV1 predicted value compared to those with FEV1/FEV6 > 73% (65.4% vs. 86.5%, p < 0.001).
Conclusion: In summary, we demonstrate that the value of 73% in FEV1/FEV6 using handheld spirometry has the best sensitivity and specificity to detect airflow limitation in subjects with risk of COPD.
Keywords: Active case finding; Pulmonary disease, chronic obstructive; Sensitivity and specificity; Spirometry.