Seroradiologic prognostic evaluation of acute exacerbation in patients with idiopathic interstitial pneumonia: a retrospective observational study

Background: We previously reported that high-resolution computed tomography (HRCT) patterns and certain serum marker levels can predict survival in patients with acute exacerbation (AE) of idiopathic pulmonary fibrosis (IPF) and in those with idiopathic interstitial pneumonias (IIPs). The utility of serum marker changes before and during AE has not been previously evaluated. This study aimed to clarify whether changes in serum marker levels could improve the prognostic significance of HRCT patterns in patients with AE-IIPs. Methods: Seventy-seven patients (60 males, 17 females) with AE-IIP diagnosed between 2004 and 2016 and whose serum Krebs von den Lungen (KL)-6 and surfactant protein (SP)-D levels were measured before and at the onset of AE were enrolled in this study. The HRCT pattern of each patient was classified as diffuse, multifocal, or peripheral. We examined the prognostic significance of the HRCT pattern, increased serum marker levels, and a combination of these parameters using Cox proportional hazard regression analysis. Results: Fifty-three patients had IPF and 24 had non-IPF IIP. A serum KL-6 level that was increased compared with the level in the stable state (Delta KL-6/ST-KL-6: <= 0.211) was a significantly poor prognostic factor in patients with a multifocal pattern. Multivariate Cox analysis identified long-term oxygen therapy, a partial oxygen tension/fraction of inspired oxygen ratio <= 200 Torr, and an elevated SP-D level during a stable state to be significantly poor prognostic factors in all patients. A diffuse HRCT pattern was not a significant prognostic factor in an AE-IIP in multivariate analysis after adjustment; however, a multifocal pattern accompanying a Delta KL-6/ST-KL-6 <= 0.211 or a diffuse pattern was a significantly poor prognostic factor than a peripheral pattern or a multifocal pattern with Delta KL-6/ST-KL-6 >0.211. Conclusions: Combining the HRCT pattern and the Delta KL-6/ST-KL-6 value can improve our ability to predict the survival of AE-IIP patients.