PURPOSE:Background: FEV1/FEV6 ratio has been suggested as a surrogate for FEV1/FVC in screening for airway obstruction in populations at high risk for COPD. However unavailability of prediction equations for FEV1/FEV6 in many countries and in portable hand-held spirometers poses difficulties in its use as a screening tool.Aim: We sought to determine a fixed cut-off of FEV1corresponding to FEV1/FVC<0.70[prescribed by guideline for obstructive lung diseases(GOLD) for detecting airway obstruction in COPD] in Indian population.
METHODS:Retrospective analysis of pulmonary function tests(PFT) of adults aged between 20–60 years performed at a tertiary referral centre in India. PFT were randomly selected and those meeting acceptability criteria were retrospectively analyzed. Receiver operator characteristic (ROC)-curve analysis and kappa-statistics were used to estimate the utility of the FEV1/FEV6 ratio in predicting an FEV1/FVC ratio < 70%.
RESULTS:Out of 500 screened PFT s, 467 were found acceptable and analysed The prevalence of airway obstruction(FEV1/FVC<0.70) in the analysed spirometries was 30.2%. ROC-curve was constructed for FEV1/FEV6 ratio compared to FEV1/FVC < 70% (area under the curve = 0.99, P < 0.0001) The value for the FEV1/FEV6 ratio which best predicted an FEV1/FVC ratio of 70%, was 73%,(youden’s index = 0.92) and a very good agreement was found between these two cut-offs (kappa = 0.89). When FEV1/FVC<0.70 is taken as the gold standard in airway obstruction screening, FEV(1)/FEV(6) sensitivity and specificity were 98 and 94.2%, respectively; the positive and negative predictive values were 88.0 and 99.4 %, respectively.
CONCLUSION:The FEV1/FEV6 <73% can be considered as a good alternative to FEV1/FVC <70% for the screening of airway obstruction.
CLINICAL IMPLICATIONS:FEV1/FEV6 <73% is a good surrogate for FEV1/FVC <70% as a screening tool for airway obstruction, due to its excellent sensitivity, negative predictive value and high reproducibility. Using a fixed cut-off for FEV1/FEV6 widens its utility in as a cheap and reliable screening tool using portable office spirometers, especially in populations where prediction equations for FEV6 are not available.
DISCLOSURE:Amit Lohia, No Financial Disclosure Information; No Product/Research Disclosure Information