Assessing two spirometric criteria of pre-bronchodilator and post-bronchodilator FEV1/FVC ratio in detecting air flow obstruction

Objectives: To assess the Pre-bronchodilator criteria and the Post-bronchodilator criteria of FEV1/FVC ratio indiagnosing Airflow obstruction.Methods: An observational study was conducted from 1988 to 2006 at the Aga Khan University Hospital.Patients referred to the pulmonary function test laboratory for spirometry with bronchodilator reversibility at thehospital during the above said period were enrolled. Forced spirometry was performed according to ATSguidelines. All patients who had pre-bronchodilator criteria of airflow obstruction were analyzed and comparedwith the post bronchodilator criteria.Results: A total of 4222 individuals underwent spirometry out of which 4072 individuals were studied.Using thepre bronchodilator criteria, 1375 (34%) patients had airflow obstruction. Applying the post bronchodilator criteriaon the same patients, 1098 (27%) had evidence of airway obstruction. Out of these 1375 patients who hadairflow obstruction by using pre-bronchodilator criteria, 277 (20%) patients had no airflow obstruction by usingthe post bronchodilator criteria. Out of these 277 patients, 52% had significant airways reversibility as evidencedby >12% increase in their FEV1 pre and post bronchodilator.Conclusion: Pre bronchodilator criteria for detection of airflow obstruction overestimate the diagnosis of airflowobstruction and by using post bronchodilator criteria for airway obstruction on spirometry, decreases this overdiagnosis of the condition.