B41-28 Interstitial Lung Disease in Systemic Autoimmune Diseases and In-hospital Outcomes: A Nationwide Analysis

Abstract Rationale Interstitial lung disease (ILD) frequently complicates systemic autoimmune diseases (SADs) -including systemic sclerosis, systemic lupus erythematosus, rheumatoid arthritis, Sjögren syndrome, vasculitis, and inflammatory myopathies-and may worsen inpatient outcomes. However, contemporary nationally representative data are limited. We evaluated the association of ILD with in-hospital outcomes among adults hospitalized with SADs using the National Inpatient Sample (NIS) from 2017-2022. Methods We conducted a retrospective cross-sectional analysis of adult SAD hospitalizations identified using ICD-10 codes in the NIS (e. g. , SLE = M32. x; systemic sclerosis = M34. x; mixed connective tissue disease/Sjögren = M35. x; polymyositis/dermatomyositis = M33. x; RA = M05-M06; vasculitis = M3x). ILD was defined by J84. x codes. The primary outcome was in-hospital mortality; secondary outcomes included length of stay (LOS), total hospital charges, and discharge disposition. Survey-weighted linear and logistic/multinomial regression models were adjusted for demographics, payer, ZIP-code income quartile, hospital characteristics (region, teaching status, and bed size), and comorbidity burden (Charlson Index). A 1: 1 propensity score-matched (PSM) analysis served as a sensitivity analysis. Results Among 1, 626, 965 SAD hospitalizations, 4, 695 (0. 29%) had ILD. Compared with non-ILD admissions, ILD was associated with a longer LOS (8. 15 vs 6. 35 days; adjusted difference +1. 60 days, 95% CI 0. 96-2. 24; p 0. 001) and higher hospital charges (110, 832 vs 79, 683; adjusted difference +28, 821, 95% CI 6, 335-51, 307; p = 0. 012). In-hospital mortality was higher among ILD admissions (3. 73% ∼175/4, 695 vs 0. 12% ∼1, 880/1, 622, 270) ; adjusted OR 1. 94 (95% CI 1. 34-2. 81; p 0. 001). Routine home discharge was less frequent (61% vs 71%), whereas discharge to other facilities was more common (adjusted RRR 1. 32, 95% CI 1. 14-1. 53; p 0. 001). Findings were directionally consistent in the PSM cohort, with higher mortality (OR 3. 72, 95% CI 3. 01-4. 59; p 0. 001), longer LOS, and higher costs among ILD admissions. Conclusions In U. S. hospitalizations for systemic autoimmune diseases, concurrent ILD is associated with significantly higher in-hospital mortality, longer LOS, greater costs, and lower rates of routine home discharge. These nationally representative findings underscore the importance of early ILD recognition and coordinated inpatient management pathways for patients with systemic autoimmune diseases. This abstract is funded by: None