Objective: Programmed death-1 (PD-1)/programmed death ligand-1 (PD-L1) exists in both membrane-bound and soluble forms. In this study, we evaluated the predictive value of soluble PD-1 (sPD-1) for severity and 28-day mortality in patients with severe sepsis and septic shock during the first week in an intensive care unit (ICU).
Methods: In this prospective cohort study, patients were classified into the severe sepsis group or the septic shock group according to the severity of their condition on ICU admission. All patients were also separated into the survivor or nonsurvivor groups according to their 28-day outcomes. Peripheral blood sPD-1 and soluble PD-L1 (sPD-L1) levels, PD-1 expression on CD4 and CD8 T cells, and PD-L1 expression on monocytes were measured and compared between the groups on days 1 and 7 after ICU admission.
Results: In all, 45 healthy volunteers and 112 patients were recruited. Serum sPD-1 levels were positively correlated with the severity of sepsis, sPD-L1 levels, PD-1 expression on CD4 or CD8 T cells, and PD-L1 expression on monocytes. The sPD-1 was an independent predictive factor for 28-day mortality both on day 1 and day 7. The area under the curve (AUC) of the sPD-1 on day 7 (0.871) was higher than that on day 1 (0.785) (P < 0.05), and better than the AUC of the percentages of PD-L1 on monocytes (0.770) on day 7 (P < 0.05).
Conclusion: Serum sPD-1 shows valuable predictive ability for the severity and 28-day mortality of severe sepsis and septic shock during the first week of ICU treatment.