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

Background . FEV 1 /FEV 6 has been proposed as a cheap, reproducible and valid alternative to FEV 1 /FVC in spirometry. No Indian data exists on its utility to diagnose airway obstruction. Aim . we sought to determine a fixed cut off of FEV 1 /FEV 6 to diagnose obstruction corresponding to FEV 1 /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 FEV 1 , FVC, FEV 6 . The sensitivity, specificity, positive and negative predictive values of FEV 1 /FEV 6 were determined with respect to gold standard of FEV 1 /FVC < 0.70. Results . 467 spirometries were analysed after meeting the ATS acceptability criteria. Considering FEV 1 /FVC < 0.7 as being the gold standard for obstruction, ROC curve was used to determine the best corresponding cut-off for FEV 1 /FEV 6 . The area under the curve was 99.3% (95% CI: 98.1–99.8%), and the FEV 1 /FEV 6 cut-off, corresponding to the greatest sum of sensitivity and specificity, was 73%. For the total population, the FEV 1 /FEV 6 sensitivity, 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 . FEV 1 /FEV 6 < 73% is a new reliable spirometry index to diagnose airway obstruction in Indian population.