Prognostic comparison of acute exacerbations across idiopathic interstitial pneumonia subtypes: A nationwide observational study.

Background: Acute exacerbations of idiopathic interstitial pneumonias (AE-IIPs) are life-threatening events. However, comparative prognostic data across IIP subtypes during AE are limited. This study aimed to evaluate in-hospital mortality differences among major AE-IIP subtypes using a nationwide database in Japan.

Methods: We retrospectively analysed patients with AE of idiopathic pulmonary fibrosis (IPF), nonspecific interstitial pneumonia (NSIP), cryptogenic organising pneumonia (COP), or acute interstitial pneumonia (AIP) who received high-dose methylprednisolone between 1 July, 2010 and 31 March, 2023. Data were extracted from the Japanese Diagnosis Procedure Combination database. The primary outcome was all-cause in-hospital mortality. Secondary outcomes included 14- and 28-day mortality. Multivariable logistic regression analysis with generalised estimating equations was employed to adjust for potential confounders, incorporating multiple imputation to address missing data.

Results: A total of 6645 patients were included (IPF, n = 2092; NSIP, n = 581; COP, n = 871; AIP, n = 3101). Unadjusted in-hospital mortality rates were 53.9 % for IPF, 40.1 % for NSIP, 17.6 % for COP, and 49.3 % for AIP. After adjustment, in-hospital mortality was significantly higher for IPF (odds ratio [OR], 3.92; 95 % confidence interval [95 % CI], 3.05-5.04; p < 0.001), NSIP (OR, 2.80; 95 % CI, 2.10-3.73; p < 0.001), and AIP (OR, 3.07; 95 % CI, 2.43-3.89; p < 0.001), compared with COP. Similar trends were observed for both secondary outcomes.

Conclusions: Among patients with AE-IIPs, those with IPF, NSIP, and AIP exhibited significantly higher in-hospital mortality compared with COP. These findings underscore the inferior prognosis associated with AE-IPF and AIP.