FEV1/FEV6: A Reliable, Easy-to-Use, and Cheaper Alternative to FEV1/FVC in Diagnosing Airway Obstruction in Indian Population

摘要

Background. FEV1/FEV6has been proposed as a cheap, reproducible and valid alternative to FEV1/FVC in spirometry. No Indian data exists on its utility to diagnose airway obstruction.Aim. we sought to determine a fixed cut off of FEV1/FEV6to diagnose obstruction corresponding to FEV1/FVC < 0.70 proposed by GOLD guidelines.Method. Spirometry was done on patient referred to a tertiary centre in India. Age, sex, height weight were recorded in addition to spirometric variables like FEV1, FVC, FEV6. The sensitivity, specificity, positive and negative predictive values of FEV1/FEV6were determined with respect to gold standard of FEV1/FVC < 0.70.Results. 467 spirometries were analysed after meeting the ATS acceptability criteria. Considering FEV1/FVC < 0.7 as being the gold standard for obstruction, ROC curve was used to determine the best corresponding cut-off for FEV1/FEV6. The area under the curve was 99.3% (95% CI: 98.1–99.8%), and the FEV1/FEV6cut-off, corresponding to the greatest sum of sensitivity and specificity, was 73%. For the total population, the FEV1/FEV6sensitivity, specificity, PPV, NPV were was 95.7 %, 94.2 %, 87.5 % and 97.9 % respectively. Agreement by Kappa value between two cut offs was excellent 0.89 (0.87–0.91).Conclusion. FEV1/FEV6< 73% is a new reliable spirometry index to diagnose airway obstruction in Indian population.