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Emphysema Complicates CT Assessment of Usual Interstitial Pneumonia, Nonspecific Interstitial Pneumonia

January 6, 2010
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The objective of a recent study was to evaluate the ability of CT to distinguish between usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP,) and to determine the effect of emphysema on the ability of CT to distinguish between the two conditions.

The study has shown that emphysema influences the ability of CT to distinguish between usual versus nonspecific interstitial pneumonia. Traction bronchiolectasis is the CT feature that best differentiates these conditions in patients with emphysema.

Design
Retrospective analysis.

Participants
42 patients with UIP and 54 patients with NSIP. The diagnosis of UIP and NSIP was made by surgical lung biopsy.

Methodology
CT scans were performed with 1.5-mm collimation at 15-mm to 20-mm intervals in full inspiration. The CT images were evaluated independently by two chest radiologists. CTs were assessed for reticulation (irregular linear opacity), ground-glass opacity, consolidation, nodules, honeycombing, and traction bronchiectasis, and bronchiolectasis.

The amount of emphysema was also assessed. Emphysema was defined as decreased attenuation, usually without walls, and nonuniform distribution causing destruction of pulmonary parenchyma.

A confident diagnosis of UIP was made if there was reticulation, extensive honeycombing, minimal ground-glass opacity, and a peripheral and basal predominance of findings.

A confident diagnosis of NSIP was made if there was no or minimal reticulation and no honeycombing but there was extensive ground-glass opacity, traction bronchiectasis, and basal predominance with subpleural sparing.

The objective of a recent study was to evaluate the ability of CT to distinguish between usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP,) and to determine the effect of emphysema on the ability of CT to distinguish between the two conditions. The study has shown that emphysema influences the ability of CT to distinguish between usual versus nonspecific interstitial pneumonia. Traction bronchiolectasis is the CT feature that best differentiates these conditions in patients with emphysema. Design Retrospective analysis. Participants 42 patients with UIP and 54 patients with NSIP. The diagnosis of UIP and NSIP was made by surgical lung biopsy. Methodology CT scans were performed with 1.5-mm collimation at 15-mm to 20-mm intervals in full inspiration. The CT images were evaluated independently by two chest radiologists. CTs were assessed for reticulation (irregular linear opacity), ground-glass opacity, consolidation, nodules, honeycombing, and traction bronchiectasis, and bronchiolectasis. The amount of emphysema was also assessed. Emphysema was defined as decreased attenuation, usually without walls, and nonuniform distribution causing destruction of pulmonary parenchyma. A confident diagnosis of UIP was made if there was reticulation, extensive honeycombing, minimal ground-glass opacity, and a peripheral and basal predominance of findings. A confident diagnosis of NSIP was made if there was no or minimal reticulation and no honeycombing but there was extensive ground-glass opacity, traction bronchiectasis, and basal predominance with subpleural sparing. [text_ad] Results The diagnosis made by the radiologist was correct 71% of the time (UIP, 55%; NSIP, 83%). The sensitivity and specificity of CT for UIP was 55% and 63%, respectively, with an accuracy of 59%. The corresponding sensitivity and specificity of CT for NSIP was 63% and 55%, respectively. In patients with superimposed emphysema, the diagnosis made by the radiologist was correct 44% of the time (UIP, 50%; NSIP, 36%). The sensitivity and specificity of CT for UIP in patients with superimposed emphysema was 50% and 36%, respectively, with an accuracy of 44%. The corresponding sensitivity and specificity of CT for NSIP in patients with superimposed emphysema was 36% and 50%, respectively. In patients with superimposed emphysema, traction bronchiolectasis was the CT characteristic that best helped differentiate UIP from NSIP. Conclusions Superimposed emphysema influences the ability of CT to distinguish between UIP and NSIP. Reviewer's Comments The authors note that there was likely a selection bias in this study because only patients with biopsy-proven interstitial lung disease were included. Patients with very typical findings of UIP on CT very often do not undergo biopsy, and therefore, this study was likely biased toward less typical findings. Author: Vineet R. Jain, MD Reference: Akira M, Inoue Y, et al. Usual Interstitial Pnuemonia and Nonspecific Interstitial Pneumonia With and Without Concurrent Emphysema: Thin-Section CT Findings. Radiology; 2009;251 (April): 271-279. [text_ad]

Results

The diagnosis made by the radiologist was correct 71% of the time (UIP, 55%; NSIP, 83%). The sensitivity and specificity of CT for UIP was 55% and 63%, respectively, with an accuracy of 59%. The corresponding sensitivity and specificity of CT for NSIP was 63% and 55%, respectively. In patients with superimposed emphysema, the diagnosis made by the radiologist was correct 44% of the time (UIP, 50%; NSIP, 36%).

The sensitivity and specificity of CT for UIP in patients with superimposed emphysema was 50% and 36%, respectively, with an accuracy of 44%. The corresponding sensitivity and specificity of CT for NSIP in patients with superimposed emphysema was 36% and 50%, respectively. In patients with superimposed emphysema, traction bronchiolectasis was the CT characteristic that best helped differentiate UIP from NSIP.

Conclusions
Superimposed emphysema influences the ability of CT to distinguish between UIP and NSIP.

Reviewer’s Comments The authors note that there was likely a selection bias in this study because only patients with biopsy-proven interstitial lung disease were included. Patients with very typical findings of UIP on CT very often do not undergo biopsy, and therefore, this study was likely biased toward less typical findings.

Author: Vineet R. Jain, MD

Reference:
Akira M, Inoue Y, et al. Usual Interstitial Pnuemonia and Nonspecific Interstitial Pneumonia With and Without Concurrent Emphysema: Thin-Section CT Findings. Radiology; 2009;251 (April): 271-279.

The objective of a recent study was to evaluate the ability of CT to distinguish between usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP,) and to determine the effect of emphysema on the ability of CT to distinguish between the two conditions. The study has shown that emphysema influences the ability of CT to distinguish between usual versus nonspecific interstitial pneumonia. Traction bronchiolectasis is the CT feature that best differentiates these conditions in patients with emphysema. Design Retrospective analysis. Participants 42 patients with UIP and 54 patients with NSIP. The diagnosis of UIP and NSIP was made by surgical lung biopsy. Methodology CT scans were performed with 1.5-mm collimation at 15-mm to 20-mm intervals in full inspiration. The CT images were evaluated independently by two chest radiologists. CTs were assessed for reticulation (irregular linear opacity), ground-glass opacity, consolidation, nodules, honeycombing, and traction bronchiectasis, and bronchiolectasis. The amount of emphysema was also assessed. Emphysema was defined as decreased attenuation, usually without walls, and nonuniform distribution causing destruction of pulmonary parenchyma. A confident diagnosis of UIP was made if there was reticulation, extensive honeycombing, minimal ground-glass opacity, and a peripheral and basal predominance of findings. A confident diagnosis of NSIP was made if there was no or minimal reticulation and no honeycombing but there was extensive ground-glass opacity, traction bronchiectasis, and basal predominance with subpleural sparing. [text_ad] Results The diagnosis made by the radiologist was correct 71% of the time (UIP, 55%; NSIP, 83%). The sensitivity and specificity of CT for UIP was 55% and 63%, respectively, with an accuracy of 59%. The corresponding sensitivity and specificity of CT for NSIP was 63% and 55%, respectively. In patients with superimposed emphysema, the diagnosis made by the radiologist was correct 44% of the time (UIP, 50%; NSIP, 36%). The sensitivity and specificity of CT for UIP in patients with superimposed emphysema was 50% and 36%, respectively, with an accuracy of 44%. The corresponding sensitivity and specificity of CT for NSIP in patients with superimposed emphysema was 36% and 50%, respectively. In patients with superimposed emphysema, traction bronchiolectasis was the CT characteristic that best helped differentiate UIP from NSIP. Conclusions Superimposed emphysema influences the ability of CT to distinguish between UIP and NSIP. Reviewer's Comments The authors note that there was likely a selection bias in this study because only patients with biopsy-proven interstitial lung disease were included. Patients with very typical findings of UIP on CT very often do not undergo biopsy, and therefore, this study was likely biased toward less typical findings. Author: Vineet R. Jain, MD Reference: Akira M, Inoue Y, et al. Usual Interstitial Pnuemonia and Nonspecific Interstitial Pneumonia With and Without Concurrent Emphysema: Thin-Section CT Findings. Radiology; 2009;251 (April): 271-279. [text_ad]
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