Predictive value of soluble programmed cell death ligand-1 in the progression of septic patients to chronic critical illness in the intensive care unit: A prospective observational clinical study.

BACKGROUND: As an immune marker, serum soluble programmed cell death ligand-1 (sPD-L1) is significantly increased in sepsis and is predictive of mortality. We investigated the prognostic value of sPD-L1 in postseptic immunosuppression and progression to chronic critical illness (CCI).

METHODS: Adults with sepsis in intensive care units (ICUs) for the first time were screened and assigned to either a chronic critical illness (CCI) group (ICU stay ≥14 days with persistent organ dysfunction) or a rapid recovery (RAP) group based on clinical outcome. Data regarding basic admission information and clinical parameters were collected and compared across the two groups. Serum sPD-L1 levels were detected by enzyme-linked immunosorbent assay at admission and on the 7th day (D7). Logistic regression analysis was used to determine the factors affecting septic patients' lymphocytopenia diagnosis on day 7 and CCI progression during hospitalization. The receiver operating characteristic (ROC) curve and DeLong test were used to assess variable predictive power.

RESULTS: During the study period, a total of 166 septic patients were admitted to the intensive care unit, and 91 septic patients were enrolled after screening. Compared to those in healthy individuals, the sPD-L1 levels in septic patients were significantly higher and positively correlated with traditional inflammatory markers and disease severity scores (P < 0.05). In a multivariate regression analysis, sPD-L1 alone predicted lymphocytopenia on day 7 (P < 0.05). In the sepsis cohort, 59 patients (64.8%) experienced RAP, and 32 patients (35.2%) developed CCI. Compared to the RAP group, the patients in the CCI group had a higher mean age, greater severity of disease, and higher mortality (P < 0.05). D7-sPD-L1 remained higher in the CCI group, and the area under the curve (AUC) that predicted the occurrence of CCI was equivalent to the APACHE II score, with AUCs of 0.782 and 0.708, respectively.

CONCLUSIONS: The severity of infection and immunosuppression in sepsis may be linked to serum sPD-L1. D7-sPD-L1 is valuable in predicting the progression of CCI in patients.