Predictive Value of Serum β2‑Microglobulin for Outcomes in Patients with Acute Respiratory Distress Syndrome Caused by Bacterial Infection

Abstract Background Acute respiratory distress syndrome (ARDS) is a heterogeneous disease with extremely high mortality. We hypothesized that the serum β2-microglobulin (β2MG) level would be elevated and be an independent risk factor for 28-day mortality in patients with ARDS. Methods We retrospectively enrolled 257 patients with ARDS caused by bacterial infection who were admitted consecutively into the Department of Pulmonary and Critical Care Medicine, Beijing Chao-Yang Hospital from January 1, 2015 to February 28, 2021. Patients were followed for up to 28 days from diagnosis and were divided into a survival group and non-survival group according to their clinical outcomes. The serum β2MG levels and other clinical data were collected. The relationship between serum β2MG levels and 28-day mortality was explored by performing a Cox regression analysis adjusted for age, updated Charlson comorbidity index, disorders of consciousness, septic shock, albumin level, cardiac troponin I level, procalcitonin level, lactic acid level, prothrombin time, and partial pressure of arterial oxygen/fraction of inspired oxygen ratio. Results In this cohort, 161 patients survived, and 96 patients died within 28 days of diagnosis, yielding a 28-day mortality of 37.4%. The median level of β2MG for all enrolled patients was 4.6 (interquartile range [IQR]: 2.9–8.5) mg/L. Higher β2MG levels were significantly associated with 28-day mortality when the β2MG level was analysed as a continuous variable (hazard ratio [HR]: 1.050; 95% confidence interval [CI]: 1.012–1.091; P = 0.010) and when it was categorized into tertiles (HR: 1.482; 95% CI: 1.069–2.045; P = 0.018). The serum β2MG level exhibited a diagnostic accuracy for predicting mortality that was not inferior to those of the Acute Physiology and Chronic Health Evaluation score (P = 0.153) and Sequential Organ Failure Assessment score (P = 0.114). Conclusions The level of serum β2MG is elevated and is an independent risk factor of 28-day mortality in patients with ARDS, suggesting that it has predictive value for the outcomes of these patients.