Impaired diffusing capacity and COPD incidence in adults with symptoms and normal spirometry.

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Epidemiology

Background:

• Impaired diffusing capacity of the lung (DLCO) without airflow obstruction is a potential marker for 'Pre-COPD'.
• The predictive value of impaired DLCO for lung function decline and COPD incidence requires further investigation.

Purpose of the Study:

• To examine the relationship between impaired DLCO and subsequent lung function decline.
• To assess the association between impaired DLCO and the incidence of COPD in adults with normal baseline spirometry.

Main Methods:

• An observational study of 266 adults aged 40-70 years with respiratory symptoms or suspected obstructive airways disease.
• Follow-up spirometry was obtained at least 12 months after the initial assessment.
• Analysis focused on individuals with normal spirometry at baseline to evaluate impaired DLCO's predictive value.

Main Results:

• No significant association was found between impaired DLCO and the annual rate of decline in post-bronchodilator FEV1, FVC, or FEV1/FVC.
• The sensitivity of impaired DLCO for COPD incidence was 40%, with a specificity of 82%.
• These findings remained consistent in subgroups of current/former smokers and when using a DLCO threshold of <80% predicted.

Conclusions:

• Impaired DLCO is not an effective discriminator of lung function decline in individuals without airflow obstruction.
• This study suggests impaired DLCO is not a reliable predictor of COPD incidence in a real-world cohort.
• Further research may be needed to identify robust biomarkers for early COPD detection.