Computed Tomography Imaging Helps Identify Diagnostic Instability of Mild-to-Moderate Chronic Obstructive Pulmonary Disease

Abstract Background: Previous studies have found that mild-to-moderate COPD may experience unstable diagnosis and fluctuations back to normal spirometry during follow-up. Whether lung structure assessment can help identify diagnostic instability of mild-to-moderate COPD remains unclear. Therefore, we designed a prospective cohort study to evaluate whether lung structure assessment can help identify diagnostic instability of mild-to-moderate COPD. Methods: Participants completed a questionnaire, prebronchodilator spirometry, postbronchodilator spirometry, inspiratory and expiratory CT scans at baseline. Mild-to-moderate COPD was defined as postbronchodilator FEV1/FVC <0.70 and postbronchodilator FEV1 ≥50% of predicted value. Patients with mild-to-moderate COPD were identified and spirometry tests were repeated 1 month, 1 year, 2 years and 3 years later. Short-term diagnostic instability was defined as postbronchodilator FEV1/FVC ≥0.70 in the first month of follow-up. Long-term diagnostic instability was defined as postbronchodilator FEV1/FVC ≥0.70 in any of the first-, second-, and third-year follow-up. Emphysema was quantified by measuring the parametric response mapping emphysema (PRMemph), which was defined as areas of lung that are less than -950 HU on inspiration and less than -856 HU on expiration. Air trapping was quantified by measuring the PRMfSAD, which was defined as areas of lung that are greater than -950 HU on inspiration but also less than -856 HU on expiration. Results: Finally, 198 participants were included in the short-term diagnostic instability dataset and 192 participants were included in the long-term diagnostic instability dataset. PRMemph identifies short-term diagnostic instability with high accuracy (AUC=0.784, 95% CI:0.711-0.858, P<0.001). For every 1% increase in PRMemph, the risk of short-term diagnostic instability (adjusted OR=0.71, 95% CI: 0.54-0.94, P<0.001) and long-term diagnostic instability (adjusted OR=0.61, 95% CI: 0.44-0.83, P<0.001) in mild-to-moderate COPD was reduced. PRMfSAD identifies short-term diagnostic instability with high accuracy (AUC=0.771, 95% CI:0.695-0.818, P<0.001). For every 1% increase in PRMfSAD, the risk of short-term diagnostic instability and long-term diagnostic instability was reduced. Conclusions: CT indicators PRMemph and PRMfSAD can be used to identify mild-to-moderate COPD diagnosis instability. In clinical practice, patients with mild-to-moderate COPD can be further evaluated by CT to identify the diagnostically stable patients and start management and intervention as soon as possible.