Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) critically affects patient survival. This study aimed to determine whether an early treatment response could accurately predict prognostic outcomes in patients with AE-IPF.

This retrospective cohort study conducted at Kobe City Medical Centre General Hospital analysed 100 patients with AE-IPF treated with steroid pulse therapy during January 2012–December 2021. The initiation day was defined as Day 1. Patients were classified into Responder or Non-Responder groups based on the changes in peripheral capillary oxygen saturation/fraction of inspired oxygen (S/F) ratios from Days 1–4. The primary outcome was 28-day mortality. Cox proportional hazards models assessed the association between 28-day mortality and potential prognostic factors, including age, KL-6 levels, S/F ratios on Day 1, and Responder group status.

The study cohort included 60 and 40 patients in the Responder and Non-Responder groups, respectively. The Responder group has significantly higher median IgG levels (1519 mg/dL vs. 1014 mg/dL) and lower mortality rates (12 % vs. 42.5 % at 28 days). On Day 1, the S/F ratios were comparable between the two groups. Similarly, age and levels of Krebs von den Lungen-6 also showed no significant differences. Multivariable Cox proportional hazards analysis revealed that higher initial S/F ratios (HR: 0.18, 95 % CI: 0.06–0.52) and classification in the Responder group (HR: 0.22, 95 % CI: 0.10–0.53) were associated with lower 28-day mortality.

Early improvements in S/F ratios may indicate improved survival in patients with AE-IPF, suggesting their potential importance in early therapeutic decisions.