Hypersensitivity pneumonitis radiologic features in interstitial lung diseases.

Background: The radiologic criteria of hypersensitivity pneumonitis (HP) guidelines focus on four HP compatible features (HPCF) in high-resolution computed tomography (HRCT): ground glass opacities, mosaic attenuation, air-trapping, and centrilobular nodules. However, evidence to support these criteria are limited.

Methods: Consecutive interstitial lung disease (ILD) patients who underwent HRCT between 2016 and 2021 in three medical centers were included. We assessed the prevalence of HPCF in each ILD and their association with HP diagnosis. We evaluated the impact of HPCF amount for HP diagnosis and the performance of the radiologic criteria by the ATS/JRS/ALAT and CHEST HP guidelines.

Results: 436 patients with ILD were included (mean age 66, 48 % females), of them, 56 (13 %) with HP. All four HPCF were more prevalent in HP than in non-HP ILD (p < 0.001 for all). In multivariate analysis, air-trapping was the strongest independent predictor (AOR 4.1, 95 % CI 2-8.4, p < 0.001). Centrilobular nodules were present almost exclusively in HP and smoking-related ILD. The amount of HPCF in HRCT had an excellent predictive ability for HP diagnosis (receiver operating characteristic AUC 0.85, 95 % CI 0.80-0.90). The radiologic criteria of both guidelines had high specificity for "typical HP" and high sensitivity for "compatible with HP", although with low positive predictive values. Our findings remained robust even when including only patients that had a diagnostic biopsy.

Conclusion: The presence and amount of HPCF in HRCT predicted HP diagnosis in real-life settings. While current HP radiologic criteria demonstrated good diagnostic performance, our findings highlight areas for future improvement.