Comparison of Clinical Measures Among Interstitial Lung Disease (ILD) Patients with Usual Interstitial Pneumonia (UIP) Patterns on High-Resolution Computed Tomography

Purpose: Idiopathic Pulmonary Fibrosis is a progressive and fatal interstitial lung disease (ILD) characterized by a typical radiographic or histologic usual interstitial pneumonia (UIP) pattern. In 2018, diagnostic categories of UIP based on computed tomography patterns were revised by the Fleischner Society. The study aimed to describe differences in comorbidities and spirometry in ILD patients that were characterized by high-resolution computed tomography (HRCT) images as having a typical, probable, indeterminate, and alternative diagnosis of UIP.

Methods: We retrospectively studied 80 ILD patients from 2017 to 2019. Typical UIP was defined using the Fleischner Society diagnostic criteria for IPF. Atypical UIP was reached by consensus after a multidisciplinary clinical-radiological-pathological review of patient data. Baseline characteristics, comorbidities, and spirometry were compared among the four subgroups.

Results: Among 80 patients, 59% were male, 61% had a history of smoking, and the mean age was 67.7 ± 10 years (SD). A typical UIP pattern was more frequently observed among patients with chronic obstructive pulmonary disease (COPD) (p < 0.001) and pulmonary hypertension (p = 0.03). Of 30 patients with COPD, 14 had emphysema, while 10 had IPF. After adjusting for forced expiratory volume in one second (FEV₁) in liters, change of FEV₁% from baseline to 6-12 months, age, and sex, only COPD remained significantly associated with typical UIP (p = 0.018). Tobacco use was not significantly associated with any radiographic type (p = 0.199).

Conclusion: Typical UIP was prevalent among COPD/emphysema patients. Although smoking has a strong association with IPF, we did not find a significant association with smoking and typical UIP in our cohort.

Keywords: Interstitial lung disease; Lung function; Usual interstitial pneumonia.