The accuracy of FEF25-75/FVC for primary classification of pulmonary function test

Introduction: FEF25-75/FVC as a spirometry parameter has been successful in early diagnosis of COPD and the methacholine challenge test. This study was performed todetermine the accuracy of FEF25-75/FVC for classification of spirometry of lung disease. Materials and Methods: Eighty subjects with clinical diagnosis of COPD and idiopathic pulmonary fibrosis (IPF) were entered into this case control study. Forty normal volunteers in the control groups with a PC20 more than 8 mg/dl were also included in this study. Spirometry, lung volumes and DLCO were measured for all subjects by the body plethysmograph. Final diagnosis of COPD and IPF were confirmed according topatient s history, the pulmonary function test, computed tomography of the lung and histopathology (in IPF subjects). The FEF25-75/FVC ratio was determined in each group and test accuracy was compared by lung volumes and DLCO as the gold standard. Results: FEF25-75/FVC was able to partition the subjects into four categories and itsagreement with the clinical diagnosis (kappa= 0.486) was more than FEV1/FVC and RV. Assessing accuracy showed that FEF25-75/FVC had the highest likelihood ratio followed by FEV1/FVC. Mid expiratory flow parameters including FEF25-75 and FEF25-75/FVC showed the highest sensitivity, positive predicted value, negative predicted value, and efficiency. Conclusion: FEF25-75/FVC is helpful in diagnosing difficult cases such as mixed type spirometry or spirometry results that are not matched with clinical findings without need of lung volume measurement.

Keywords:

COPD , Dysanapsis , FEF25-75/FVC , Idiopathic pulmonary fibrosis , MMEF/FVC , Spirometry.