Predictors of one-year interstitial lung disease progression in patients with interstitial pneumonia with autoimmune features: a single-center, prospective study

INTRODUCTION: Interstitial pneumonia with autoimmune features (IPAF) describes a rare condition characterized by interstitial lung disease (ILD) with autoimmune manifestations in the absence of defined autoimmune rheumatic diseases (AIRDs). Although the classification was established in 2015, prospective data on the disease progression remain limited. OBJECTIVES: Our aim was to identify predictors of ILD progression in IPAF patients using 3 criteria: 1) progressive pulmonary fibrosis (PPF); 2) INBUILD criteria; and 3) absolute forced vital capacity (FVC) decline by 10% or more. A secondary aim was to compare bronchoalveolar lavage fluid (BALF) cellular profiles in patients with IPAF and AIRD‑ILD and explore a prognostic value of these profiles. PATIENTS AND METHODS: Between March 2021 and November 2022, a total of 69 patients were prospectively recruited: 31 with IPAF and 38 with AIRD‑ILD. Clinical, laboratory, radiological, pulmonary function, and BALF data were analyzed. Univariable and multivariable logistic regression were used to assess 1‑year progression predictors. RESULTS: Among the IPAF patients, 43.3% met the PPF criteria, 36.7% met the INBUILD criteria, and 22.2% showed FVC decline by 10% or more. PPF‑defined progression was more frequent in the IPAF than AIRD‑ILD individuals (43.3% vs 19.35%; P = 0.04). Progression predictors per the PPF criteria included elevated peripheral blood neutrophil count (odds ratio [OR], 1.89; 95% CI, 1.08-3.31; P = 0.03) and usual interstitial pneumonia pattern on high‑resolution computed tomography (HRCT; OR, 43.8; 95% CI, 1.52-126; P = 0.03). BALF lymphocyte count was not associated with progression (OR, 1.1; 95% CI, 0.99-1.22; P = 0.07). For the INBUILD criteria, the predictors were peripheral blood neutrophil count (OR, 2.06; 95% CI, 1.19-3.59; P = 0.01) and honeycombing (OR, 69.1; 95% CI, 2.16-2220; P = 0.02). Antinuclear antibody titer had no impact on IPAF progression. CONCLUSIONS: Fibrotic features on HRCT (usual interstitial pneumonia, honeycombing) and peripheral neutrophilia were predictors of short‑term ILD progression in IPAF.