Thin-section CT in obstructive pulmonary disease: discriminatory value

To use thin-section computed tomography (CT) to distinguish between causes of obstructive pulmonary disease, to determine which distinctions give rise to diagnostic imprecision, and to identify the most useful CT features.

Thin-section CT scans of 105 patients with obstructive pulmonary disease (asthma, n = 35; centrilobular emphysema, n = 30; panlobular emphysema, n = 21; and obliterative bronchiolitis, n = 19) and 33 healthy subjects were assessed independently by two observers. The most likely diagnosis and a confidence rating were assigned. Individual thin-section CT features were recorded. Accuracy, sensitivity, specificity, negative predictive value, and positive predictive value for first-choice diagnoses were calculated. The prevalence of CT features between pairs of conditions was compared with the chi(2) or Fisher exact test as appropriate.

A correct first-choice diagnosis was made in 199 of 276 (72%) observations. A correct first-choice diagnosis was made in 35 of 38 (92%) observations in patients with obliterative bronchiolitis, in 53 of 60 (88%) observations in patients with centrilobular emphysema, in 53 of 66 (80%) observations in healthy subjects, in 37 of 70 (53%) observations in patients with asthma, and in 20 of 42 (48%) observations in patients with panlobular emphysema. The major sources of diagnostic inaccuracy were differentiation between panlobular and centrilobular emphysema, asthma and normality, and asthma and obliterative bronchiolitis. There were significant increases in prevalence of (a) bronchial wall thickening and vascular attenuation in patients with asthma when compared with healthy subjects and (b) vascular attenuation and decreased attenuation in patients with obliterative bronchiolitis when compared with patients with asthma (P <.001).

CT helps to distinguish diseases that cause airflow obstruction. Thin-section CT is particularly accurate in the identification of obliterative bronchiolitis.