Usual Interstitial Pneumonia and Nonspecific Interstitial Pneumonia with and without Concurrent Emphysema: Thin-Section CT Findings

Masanori Akira, MD Yoshikazu Inoue, MD Masanori Kitaichi, MD Satoru Yamamoto, MD Toru Arai, MD Kazushige Toyokawa,

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 reading 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.