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Year : 2019  |  Volume : 21  |  Issue : 3  |  Page : 175-181

The effectiveness of lower limit of normal criteria and cutoff rate of forced expiratory volume in 1 s/forced expiratory volume in 6 s using in the diagnosis of airway obstruction in chronic obstructive pulmonary disease patients diagnosed with fixed ratio

Department of Chest Disease, Anadolu Health Center Hospital, Kocaeli, Turkey

Correspondence Address:
Mr. Gokhan Erdogan
Department of Chest Diesease Pulmonary Function Laboratory, American Hospital, Istanbul
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ejop.ejop_78_18

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AIMS: The definition of limited airflow as forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio for chronic obstructive pulmonary disease (COPD) is still controversial. The objective of this study was to compare the prevalence of COPD using fixed ratio and lower limit of normal (LLN) of FEV1/FVC for the presence of airflow limitation and evaluate the performance of FEV1/forced expiratory volume in 6 s (FEV6) in patients diagnosed with COPD according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) fixed ratio. SUBJECTS AND METHODS: Patients who presented to the pulmonary disease clinic between May 2008 and December 2017 and who were diagnosed with COPD were evaluated retrospectively. The distribution of FEV1/FVC-LLN according to the GOLD fixed ratio was evaluated after the patients were divided based on age groups. A receiver operating characteristics curve was used to determine the best FEV1/FEV6 cutoff value which fit into the FEV1/FVC <LLN, and sensitivity and specificity were calculated. RESULTS: Of the patients, 165 (85.9%) were male and 27 were female, with a mean age of 64.40 ± 10.66 years (range, 40–85). Among the patients, 11.5% of 61 patients aged 40–60 years, 28.4% of 67 patients aged 61–70 years, and 26.6% of 64 patients aged over 70 years were out of the diagnosis of obstruction according to the fixed ratio of FEV1/FVC >LLN. The cutoff value of FEV1/FEV6 for airway obstruction according to FEV1/FVC <LLN was 0.735 with a sensitivity of 99.3%, a specificity of 95.3%, and area under the curve of 0.900 (95% confidence interval: 0.856–0.944, P < 0.001). CONCLUSIONS: In this study, older patients, particularly, were diagnosed less often with an FEV1/FVC <LLN value calculated according to the Global lung function initiative (GLI) norms, compared to the fixed ratio. In addition, ratio of FEV1/FEV6 of < 0.735 may be useful in the diagnosis of airway obstruction in the early period and may also be used in office-type spirometers, since it is not dependent on a time constant.

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