The Associations of Serum IL-37 With the Severity and Prognosis in Patients With Community-Acquired Pneumonia: A Retrospective Cohort Study

Abstract

Background: Recent evidences suggested that IL-37 may participate in the pathophysiology of community-acquired pneumonia (CAP). Nevertheless, its exact biological role was unknown. The objective of this study was to determine the associations of serum IL-37 with the severity and prognosis in CAP patients based on a retrospective cohort study.

Methods: The whole of 120 healthy subjects and 240 CAP patients were summoned. Peripheral blood was collected and IL-37 was detected using ELISA.

Results: Serum IL-37 was obviously decreased in CAP patients on admission. In addition, serum IL-37 was gradually decreased in parallel with CAP severity scores. Correlative analysis revealed that serum IL-37 was negatively associated with CAP severity scores and inflammatory cytokines. Further logistical regression found that reduction of serum IL-37 augmented the severity of CAP patients. Moreover, the follow-up research was performed in CAP patients. Serum lower IL-37 on admission prolonged the hospital stay in CAP patients. Serum IL-37 combination with PSI and CURB-65 had a stronger predictive capacity for death than IL-37 and CAP severity score alone in CAP patients.

Conclusion: There are remarkably negative correlations between serum IL-37 with the severity and prognosis in CAP patients. Serum IL-37 on admission prolongs the hospital stay, demonstrating that IL-37 may involve in the process of CAP. Serum IL-37 may be regarded as a biomarker for diagnosis and prognosis for CAP patients.

Keywords: IL-37; biomarker; community-acquired pneumonia; community-acquired pneumonia severity score; inflammatory cytokine.

Figure 1

Flow diagram of recruitment and follow-up study in CAP patients.

Figure 2

The levels of serum IL-37 in No-CAP and CAP cases. (A–F) The level of serum IL-37 was detected with ELISA. (A) The level of serum IL-37 in CAP patients and control subjects. (B) The level of serum IL-37 in different ranks of CRB-65 score of CAP. (C) The level of serum IL-37 in different ranks of SMART-COP score of CAP. (D) The level of serum IL-37 in different ranks of CURXO score of CAP. (E) The level of serum IL-37 in different ranks of SMART-COP score of CAP. (F) The level of serum IL-37 in different ranks of PSI score of CAP. *P < 0.05, **P < 0.01.

Figure 3

The levels of serum IL-37 in alive and dead CAP patients. (A, B) The level of serum IL-37 was detected with ELISA. (A) The level of serum IL-37 in alive and dead CAP patients. (B) The level of serum IL-37 in different hospital stay of CAP patients. *P < 0.05, **P < 0.01.

Figure 4

Receiver operating characteristic curves for different predictive biomarkers on admission. (A) ROC curve was used to evaluate the severity of different predictive biomarkers for CAP. (B) ROC curve was used to evaluate the death risk of different predictive biomarkers for CAP. (C) ROC curve was used to evaluate the death risk of serum IL-37 combination with CAP severity scores.