Chronic Hypersensitivity Pneumonitis: Differentiation from Idiopathic Pulmonary Fibrosis and Nonspecific Interstitial Pneumonia by Using Thin-Section CT

C. Isabela S. Silva, MD, PhD Nestor L Muller, MD, PhD David A. Lynch, MD Douglas Curran-Everett, PhD Kevin K. Brown, MD Kyung Soo Lee, MD Man Pyo Chung, MD Andrew Churg, MD

Purpose: To retrospectively determine if the interval increase of right ventricular-left ventricular (RV/LV) diameter ratio from negative prior to positive current computed tomographic (CT) examination findings for pulmonary embolism (PE) is more accurate for predicting 30-day mortality than positive CT ratio alone, by using patient 30-day mortality as reference standard.

Materials and Methods: This retrospective study was approved by the institutional research boards of the participating centers, and informed consent was waived. There was H1PAA compliance for all U.S. patients. The study included 66 patients (36 men, 30 women; mean age, S8.8 years � 10.9 [standard deviation])with proved chronic HP (n = 18), IPF (n = 23), or NSIP (n = 25) who underwent CT. Two independent read ers assessed the CT images, made a first-choice diagnosis, and noted the degree of confidence in the diagnosis. A general linear model was used to identify CT features that independently differentiated chronic HP from IPF and NSIP. Weighted K statistic was used to assess interob-server agreement.

Results:The CT features that best differentiated chronic HP were lobular areas with decreased attenuation and vascularity, centrilobular nodules, and absence of lower zone predominance of abnormalities (P

Conclusion: Characteristic CT features of chronic HP, IPF, and NSIP allow confident distinction between these entities in approximately 50% of patients.