Usual interstitial pneumonia and nonspecific interstitial pneumonia with and without concurrent emphysema: thin-section CT findings.

PURPOSE: To determine whether concurrent emphysema influences the distinction between usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP) at thin-section computed tomography (CT).

MATERIALS AND METHODS: Institutional review board approval was obtained for this retrospective study; informed consent was not required. The study included 54 patients with NSIP and 42 patients with UIP (55 men, 41 women; mean age, 60.2 years +/- 9.2 [standard deviation]; age range, 33-77 years). Two independent readers assessed the CT images and made a first-choice diagnosis. The appearances of UIP and NSIP at CT were compared with univariate and multivariate analyses. Receiver operating characteristic curves were used to determine how concurrent emphysema influences the distinction of UIP from NSIP at thin-section CT.

RESULTS: The diagnosis was correct in 136 (71%) of 192 readings. In patients with concurrent emphysema, the diagnosis was correct in 30 (44%) of 68 readings. Sensitivity, specificity, and accuracy for diagnosis were lower in patients with concurrent emphysema than in patients without concurrent emphysema. In patients with concurrent emphysema, there were no significant differences in extent of fibrosis, extent of honeycombing, extent of consolidation, coarseness of fibrosis score, extent of traction bronchiectasis, upper lung irregular lines, peribronchovascular distribution, and nodules between UIP and NSIP. According to multivariate analysis, the CT feature that helped best differentiate UIP from NSIP in patients with emphysema was traction bronchiolectasis.

CONCLUSION: Concurrent emphysema influenced the distinction between UIP and NSIP.