Chronic hypersensitivity pneumonitis: differentiation from idiopathic pulmonary fibrosis and nonspecific interstitial pneumonia by using thin-section CT.
OBJECTIVE
To retrospectively assess the accuracy of thin-section computed tomography (CT) in distinguishing chronic hypersensitivity pneumonitis (HP) from idiopathic pulmonary fibrosis (IPF) and nonspecific interstitial pneumonia (NSIP), with histologic results as the reference standard.


METHODS
This retrospective study was approved by the institutional research boards of the participating centers, and informed consent was waived. There was HIPAA compliance for all U.S. patients. The study included 66 patients (36 men, 30 women; mean age, 58.8 years +/- 10.9 [standard deviation]) with proved chronic HP (n = 18), IPF (n = 23), or NSIP (n = 25) who underwent CT. Two independent readers 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 kappa statistic was used to assess interobserver 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 < or = .008). The features that best differentiated NSIP were relative subpleural sparing, absence of lobular areas with decreased attenuation, and lack of honeycombing (P < or = .002). The features that best differentiated IPF were basal predominance of honeycombing, absence of relative subpleural sparing, and absence centrilobular nodules (P < or = .004). A confident diagnosis was made in 70 (53%) of 132 readings. This diagnosis was correct in 66 (94%) of 70 readings. The accuracy for the entire cohort was 80%. Interobserver agreement for confident diagnosis was good to excellent (kappa = 0.77-0.96).


CONCLUSIONS
Characteristic CT features of chronic HP, IPF, and NSIP allow confident distinction between these entities in approximately 50% of patients.
Silva
C Isabela S
CI
Department of Radiology, Vancouver General Hospital, University of British Columbia, 3350-950 W 10th Ave, Vancouver, BC, Canada V5Z 4E3. isabela.silva@vch.ca
Müller
Nestor L
NL
Lynch
David A
DA
Curran-Everett
Douglas
D
Brown
Kevin K
KK
Lee
Kyung Soo
KS
Chung
Man Pyo
MP
Churg
Andrew
A
D000328:Adult; D000368:Aged; D000542:Alveolitis, Extrinsic Allergic / Q000000981:diagnostic imaging*; D002908:Chronic Disease; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011658:Pulmonary Fibrosis / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods