Accuracy of lung function parameters to predict COPD later in life

Abstract

Abstract Background: Chronic Obstructive Pulmonary Disease (COPD) is a common respiratory condition, characterised by chronic airflow obstruction (CAO), which is linked with significant morbidity and mortality. Early identification of individuals at risk of developing COPD is essential for timely interventions and improved outcomes. Pulmonary Function Tests (PFTs), specifically the assessment of the ratio of the forced expiratory volume in the first one second to the forced vital capacity of the lungs (FEV1/FVC ratio), have demonstrated notable potential in predicting the onset of COPD. However, the optimal threshold of FEV1/FVC to discriminate COPD and assess the risk of COPD remains unclear. Objective: To identify the optimal threshold of FEV1/FVC to discriminate COPD and assess the risk of COPD based on the new FEV1/FVC threshold. Methods: I used data from the Burden of Obstructive Lung Disease (BOLD) cohort, which is a prospective study of adults, over the age of 40 years, in a globally distributed sample of 18 sites. I estimated the prevalence of CAO, defined as a postbronchodilator FEV1/FVC ratio less than the lower limit of normal (LLN), using data from 3,945 participants. I then identified the optimal FEV1/FVC threshold by calculating the Youden Index and the Area Under the Receiver Operating Characteristic Curve (AUC) graph, and then analysed the association between being below the threshold and developing obstruction later at follow-up time. I used CAO as a proxy for COPD. Results: Among the 3,945 participants, 3,665 (92.9%) had no CAO at baseline, while 162 (4.1%) developed CAO later. Females constituted 56.3% of the participants, with males averaging 52 years and females averaging 51 years in age. The logistic regression revealed that one unit increase in the z-score for FEV1/FVC was associated with 73% lower odds of developing obstruction. The Youden Index, sensitivity, and specificity values indicated moderate performance, with values of 0.52, 0.74, and 0.77, respectively. The appropriate cut-off threshold was -0.66, which corresponds to the 25.5th percentile of the FEV1/FVC ratio. The model exhibited strong discriminative power with an AUC of 0.80. Individuals below the threshold of -0.66 had a 6.4 times greater chance of developing obstruction, with a 95% confidence interval of 3.24 to 12.65. Conclusion: The determined optimal threshold for the FEV1/FVC ratio is -0.66, approximately 25.5%, which indicates a higher risk of developing of CAO and offers a direct approach for early detection and intervention of COPD.