Cryptogenic organizing pneumonia (COP) is a form of non-specific lung injury characterized by the formation of alveolar granulomas. While it typically responds well to glucocorticoid therapy, the condition is prone to relapse upon dose reduction or discontinuation of treatment. Recurrence of COP is associated with a poor prognosis and significantly impacts patients' quality of life. Consequently, analyzing the clinical characteristics and identifying risk factors for recurrence are crucial for early recognition and minimizing the likelihood of relapse.

By analyzing the clinical data of patients with COP, we aim to identify potential risk factors associated with disease recurrence. This research will enhance the understanding of COP recurrence mechanisms and provide valuable insights for clinical doctors to develop more effective prevention strategies.

We retrospectively collected data from 95 patients who were diagnosed with COP through a combination of clinical, radiological, and pathological assessments at the Affiliated Central Hospital of Shandong First Medical University from 2014 to 2023. All patients were followed up at 1, 3, and 6 months after discharge, with the results interpreted jointly by specialized pulmonologists and radiologists. Patients were divided into two groups based on recurrence status: the recurrence group and the non-recurrence group. We analyzed the general information, clinical manifestations, laboratory tests, and imaging findings of the two groups. Univariate analysis was performed, and significant indicators were further subjected to multivariate Logistic regression analysis to identify independent risk factors for COP recurrence.

A total of 95 patients with COP were included in this study, comprising 49 males and 46 females, with ages ranging from 18 to 85 years. The main clinical manifestations were dry cough, chest tightness, dyspnea, and respiratory distress. Chest imaging primarily showed multifocal or large areas of consolidation in both lungs. Laboratory tests showed no significant specificity, but some patients had elevated inflammatory markers, including white blood cell count, neutrophil count, C-reactive protein, and erythrocyte sedimentation rate. Pathological findings included granulation tissue formation in the alveolar ducts and alveolar spaces, often accompanied by massive accumulation of foamy macrophages, inflammatory cell infiltration, alveolar epithelial proliferation, fibrous tissue proliferation, and widened alveolar septa. Among the 95 patients, 24 experienced recurrence. Univariate analysis revealed that white blood cell count, neutrophil count, C-reactive protein, alanine aminotransferase, lactate dehydrogenase, γ-glutamyl transferase (γ-GT) , erythrocyte sedimentation rate, arterial oxygen partial pressure, time from onset to diagnosis, and fever were associated with COP recurrence. Multivariate Logistic regression analysis identified higher lactate dehydrogenase (OR=1.003, 95%CI=1.003-1.037, P=0.024) , higher erythrocyte sedimentation rate (OR=1.084, 95%CI=1.037-1.132, P=0.002) , lower arterial oxygen partial pressure (OR=0.882, 95%CI=0.817-0.952, P=0.001) , and longer time from onset to diagnosis (OR=1.017, 95%CI=1.003-1.031, P=0.016) as independent risk factors for COP recurrence.

Higher lactate dehydrogenase, higher erythrocyte sedimentation rate, lower arterial oxygen pressure, and longer time from onset to diagnosis are independent risk factors for COP recurrence.