Clinical Significance of Intra-alveolar Fibrin Deposition in Transbronchial Lung Biopsy in Patients with Organizing Pneumonia

This study examined the clinical significance of intra-alveolar fibrin deposition (IAFD) in transbronchial lung biopsy specimens obtained from patients with organizing pneumonia. Pathological reports of transbronchial lung biopsies performed between 2004 and 2012 were reviewed to identify cases of intra-alveolar organization with or without fibrin deposition. Clinical charts, computed tomography images, and transbronchial lung biopsy specimens from these cases were examined retrospectively. Diagnosis of organizing pneumonia was reevaluated based upon the consensus of a respiratory physician, a radiologist, and a pathologist. Transbronchial lung biopsy results of the reviewed patients with organizing pneumonia found seven patients who had IAFD, and 34 who did not. Seven patients' conditions were associated with collagen vascular disease (CVD), and 34 were cryptogenic. IAFD was significantly associated with high C-reactive protein (CRP) values (> 5 mg/dl) (p = 0.0012) and underlying CVD (p = 0.0099). Multivariate analysis revealed that IAFD was independently associated with high CRP values (p = 0.0184). Three of 31 patients and six of 27 patients experienced a relapse of organizing pneumonia within 6 months and 1 year, respectively. IAFD (p = 0.0044) and high CRP values (p = 0.0207) were significantly related to relapse within 6 months, while only CRP was significantly related to relapse within 1 year (p = 0.0007). In patients with organizing pneumonia, IAFD was significantly associated with high CRP values. High CRP values and/or IAFD predicted relapse of organizing pneumonia within 6 months to 1 year.