Role of C5aR2 in prognosis of patients with acute respiratory distress syndrome through negative modulation of C5a: A prospective observational study

Objective: Diverse inflammatory pathology is involved in acute respiratory distress syndrome (ARDS). This study aimed to assess the role of complement component fragment 5a (C5a) receptor 2 (C5aR2) in prognosis of patients with ARDS. Methods: A total of 64 adult patients diagnosed with ARDS were prospectively recruited to the study over a period of one year after obtaining the informed consent. The serum C5a and C5aR2were determined using ELISA Kit sandwich method. Area under receiver operating characteristic (AUROC) was used to analyse the prognostic performance of C5a, C5R2, and C5a/C5R2 ratio using MedCalc. The relationship of these biomarkers with the parameters of poor prognosis (non-recovery, hospitalization, ventilation and ICU admission) was analysed through regression using SPSSv20. Results: The mean age of the included participants was 49.17 (SD:14.81) years. C5a/C5aR2 ratio had better discrimination (AUC: 0.707 vs 0.699 vs 0.511) and higher specificity (78.1 vs 71.9 vs 3.1) than C5R2 and C5a in predicting the poor prognosis among ARDS patients. The increased level of C5aR2 (OR: 0.225; p = 0.009) was significantly associated with better recovery and the high C5a/C5aR2 ratio (OR: 3.281; p = 0.036) was significantly associated with non-recovery in moderate to severe patients. Additionally, steroid treatment significantly associated with better recovery in patients with a high C5a/C5aR2 ratio (OR: 0.104; p = 0.007). Conclusion: The current evidence indicates that a higher levels of C5aR2 significantly associated with better recovery, whereas high levels of C5a/C5aR2 significantly associated to poor prognosis in moderate to severe ARDS patients. However, adequately powered studies are required to confirm these findings in future.