Exploring the role of autoimmune conditions in acute interstitial pneumonia.

Abstract

Clinical factors influencing outcomes of patients hospitalized with acute interstitial pneumonia (AIP) is not well described due to the condition's rarity. Do patients with AIP and autoimmune conditions differ from AIP patients without autoimmune conditions in mortality, recurrence, mechanical ventilation, discharge disposition, and length of hospital stay? Retrospective cohort study using U.S. MarketScan and Medicare claims (2016-2023). Diagnoses were identified using ICD-10 codes. Outcomes included in-hospital, 90- and 180-day mortality (Medicare only), AIP recurrence, mechanical ventilation within 30 days, discharge disposition, and length of stay. Multivariable logistic and negative binomial regression compared outcomes by autoimmune status, adjusting for demographics and geography. The study included 4,726 Medicare patients and 975 MarketScan patients; 20% had an autoimmune condition. Medicare patients with autoimmune conditions had significantly lower odds of 90-day mortality (OR: 0.85; 95%CI: 0.74-0.99), higher odds of discharge home (OR: 1.18; 95%CI: 1.02-1.36), and lower odds of discharge to a skilled nursing facility (OR: 0.77; 95%CI: 0.61-0.97). Length of stay, recurrence, mechanical ventilation, and results from MarketScan did not significantly differ by autoimmune status. Medicare AIP patients with autoimmune conditions had lower 90-day mortality and more favorable discharge disposition, while other outcomes were similar. These differences may reflect a subgroup characterized by greater engagement with specialty care and differential treatment approaches. Future work is needed to identify factors associated with better AIP outcomes to inform more effective care.