Abstract Rationale Hypersensitivity pneumonitis (HP) is a heterogeneous interstitial lung disease (ILD) that results from an immunological response to inhaled antigens in susceptible individuals. Sustained antigen exposure can lead to chronic airways disease, interstitial inflammation, and eventual fibrosis. Small airways disease (SAD) is a known hallmark of HP both radiographically and histologically but is difficult to quantify with traditional pulmonary function testing (PFT) and serology. Here we explore the use of quantitative computed tomography (qCT) imaging to identify SAD in patients with imaging consistent with a typical HP pattern. We hypothesize that patients with a diagnosis of HP exhibit greater airway wall thickening consistent with SAD as compared to patients with alternative diagnoses. Methods We retrospectively identified all patients presented at our institution’s ILD Multidisciplinary Discussion Conference (MDD) over a two-year period with radiological findings suggestive of typical HP, as determined by a thoracic radiologist. Patients were then diagnosed by the MDD as either “Definite or Probable HP” (N = 25) or “Alternative to HP” (N = 4). All patients labeled as “Alternative to HP” were diagnosed with systemic autoimmune rheumatic disease (SARD) ILD. Electronic medical record data was collected including laboratory testing, PFT, and imaging results within a one-year period of diagnosis. Quantitative Chest CT parameters of each group were anlayzed using AVIEW LCS + (Coreline Soft, Co. ltd, Seoul, Korea), including the square root of the airway wall area at a standard 10 mm inner perimeter (AWT- Pi10), airway wall thickness of the whole lung and smaller bronchi (5th and 6th generation), and lung texture analysis. Non-parametric data was analyzed using Independent-samples Mann-Whitney U testing. Results Patients with Definite or Probable HP had a trend toward greater whole lung AWT Pi10 compared to the alternative diagnosis group (5.6 vs 4.45 mm2; p = 0.051). Measured airway wall thickness at the sixth bronchus generation was significantly greater in the HP group (2.9 vs 2.05 mm, p = 0.025). No statistically significant differences were observed in the degree of quantitative fibrosis, serological parameters, or PFT data between the two groups. Conclusions Amongst patients with a typical HP radiographic pattern, only the patients with Definite or Probable HP exhibit increased airway wall thickness on qCT independent of the degree of fibrosis, suggesting the presence of SAD. These findings suggest a role for qCT parameters such as airway wall thickness in diagnosing HP. This abstract is funded by: None
Talento et al. (Fri,) studied this question.