Hypersensitivity Pneumonitis on Thin-Section Chest CT Scans: Diagnostic Performance of the ATS/JRS/ALAT versus ACCP Imaging Guidelines

Abstract

Purpose To compare the diagnostic performance of the American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax (ATS/JRS/ALAT) versus the American College of Chest Physicians (ACCP) imaging classifications for hypersensitivity pneumonitis (HP). Materials and Methods Patients in the institutional review board-approved Interstitial Lung Disease (ILD) registry referred for multidisciplinary discussion (MDD) at the authors' institution (January 1, 2006-April 1, 2021) were included in this retrospective study when ILD was diagnosed at MDD. MDD diagnoses included HP, connective tissue disease-ILD, and idiopathic pulmonary fibrosis. Retrospective review of thin-section CT images was performed in consensus by two cardiothoracic radiologists blinded to the diagnosis. Diagnostic patterns were determined for thin-section CT images using both classifications. Discordance rates were determined. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were assessed using MDD diagnosis as the reference standard. Results A total of 297 patients were included in the study: 200 (67%) with HP, 49 (16%) with connective tissue disease-ILD, and 48 (16%) with idiopathic pulmonary fibrosis at MDD. The discordance rate between the two classifications was 21%. Assuming low HP prevalence (10%), ATS/JRS/ALAT classification outperformed ACCP classification, with greater accuracy (92.3% vs 87.6%) and greater positive predictive value (60.7% vs 42.9%). Assuming high prevalence (50%), accuracy and negative predictive value were superior using ACCP classification (81.7% vs 79.7% and 77.7% vs 72.6%, respectively), and positive predictive value was superior using ATS/JRS/ALAT classification (93.3% vs 87.1%). Conclusion Accuracy of the ATS/JRS/ALAT and ACCP HP classifications was greater in settings with low and high HP prevalence, respectively. Diagnostic performance of both classifications was discordant in a minority of cases. Keywords: CT, Thorax, Hypersensitivity Pneumonitis, Interstitial Lung Disease Supplemental material is available for this article. © RSNA, 2024.

Keywords: CT; Hypersensitivity Pneumonitis; Interstitial Lung Disease; Thorax.

Graphical abstract

Figure 1:

Inspiratory (A) axial and (C) sagittal CT images in the lung window in a 76-year-old woman show lower lung and peripheral predominant reticulation (circle, A and C) and traction bronchiectasis (arrow, A). (B) Expiratory axial CT image shows air trapping (dashed circle, B). Diagnostic patterns were typical hypersensitivity pneumonitis per ACCP and compatible hypersensitivity pneumonitis per ATS/JRS/ALAT guidelines. A higher level of confidence could not be reached with ATS/JRS/ALAT given lower lobe distribution. A diagnosis of fibrotic hypersensitivity pneumonitis was made during multidisciplinary discussion. ACCP = American College of Chest Physicians, ATS/JRS/ALAT = American Thoracic Society/Japanese Respiratory Society/Asociación Latinoamericana del Tórax.

Figure 2:

(A) Inspiratory axial, (B) expiratory axial, and (C) sagittal CT images in a lung window in a 61-year-old woman show lower lobe predominant ground-glass opacity with reticulation (dashed circles, A and C), traction bronchiectasis (long arrows, A and C), and subpleural reticulation with honeycombing (arrowheads, A) (short arrow, C). Inspiratory mosaicism (white circle, A) is associated with air trapping on expiratory axial CT image (white circles, B). The combination of ground-glass opacity indicative of infiltration and fibrosis, mosaicism indicative of air trapping, and intervening normal parenchymal attenuation constitute the three-attenuation pattern. Diagnostic patterns were typical hypersensitivity pneumonitis per ACCP and compatible hypersensitivity pneumonitis per ATS/JRS/ALAT guidelines. A higher level of confidence could not be reached with ATS/JRS/ALAT given lower lobe predominance. A diagnosis of fibrotic hypersensitivity pneumonitis was made during multidisciplinary discussion. ACCP = American College of Chest Physicians, ATS/JRS/ALAT = American Thoracic Society/Japanese Respiratory Society/Asociación Latinoamericana del Tórax.

Figure 3:

Inspiratory (A) axial and (C) sagittal CT images in the lung window in a 28-year-old man show basilar and peribronchovascular predominant ground-glass opacity (black circles, A and C) and subtle traction bronchiectasis (arrow, A) with nonprofuse ground-glass nodularity (white circles, A and C). (B) There is no air trapping on the expiratory axial CT image. Diagnostic patterns were compatible hypersensitivity pneumonitis per ACCP and indeterminate hypersensitivity pneumonitis per ATS/JRS/ALAT guidelines. A higher level of confidence could not be reached with ATS/JRS/ALAT given lower lobe distribution of nonprofuse ground-glass opacity in a nonusual interstitial pneumonia pattern. A diagnosis of connective tissue disease–interstitial lung disease was made during multidisciplinary discussion. ACCP = American College of Chest Physicians, ATS/JRS/ALAT = American Thoracic Society/Japanese Respiratory Society/ Asociación Latinoamericana del Tórax.