Objective:To investigate the prognostic value of proprotein convertase subtilisin/kexin type 9 (PCSK9) and blood lipid indexes in patients with sepsis.Methods:Patients with sepsis or septic shock who were ≥ 18 years old and met the Sepsis-3.0 diagnostic criteria admitted to the department of critical care medicine of Binzhou Medical University Hospital from January to October 2021 were enrolled. Healthy adults at the same period were selected as healthy control group. Baseline characteristics, acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) and sequential organ failure assessment (SOFA) score were recorded. Venous blood samples were collected within 24 hours after diagnosis, and serum PCSK9 was determined by enzyme-linked immunosorbent assay (ELISA) at 1, 3 days and 5 days. Meanwhile, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglyceride (TG) and lipoprotein A were detected. The differences of each index between sepsis group (28-day death group and survival group) and healthy control group were compared. Meanwhile, the indexes of patients with different severity and 28-day prognosis in sepsis group were compared. Receiver operator characteristic curve (ROC curve) was drawn to evaluate the predictive value of PCSK9 and blood lipid for the prognosis of sepsis. Multivariate Logistic regression was used to analyze the influencing factors for the prognosis of sepsis, and the Kaplan-Meier survival curve at 28th day was drawn.Results:There were 50 patients in sepsis group (including 19 patients with sepsis, 31 patients with septic shock) and 27 patients in healthy control group. In the sepsis group, 19 patients died and 31 patients survived within 28 days. The serum PCSK9 in the sepsis group was significantly higher than that in the healthy control group [μg/L: 223.09 (198.47, 250.82) vs. 188.00 (165.27, 214.90), P < 0.01], and HDL-C, LDL-C, TC and lipoprotein A were significantly lower than those in the healthy control group [HDL-C (mmol/L): 0.82±0.35 vs. 1.45±0.24, LDL-C (mmol/L): 1.53 (1.14, 2.47) vs. 2.89 (2.55, 3.19), TC (mmol/L): 2.03 (1.39, 2.84) vs. 4.24 (3.90, 4.71), lipoprotein A (g/L): 8.80 (5.66, 17.56) vs. 27.03 (14.79, 27.03), all P < 0.01]. PCSK9 in the sepsis death group was higher than that in the survival group [μg/L: 249.58 (214.90, 315.77) vs. 207.01 (181.50, 244.95), P < 0.01], and the HDL-C, LDL-C and TC were lower than those in the survival group [HDL-C (mmol/L): 0.64±0.35 vs. 0.93±0.30, LDL-C (mmol/L): 1.32±0.64 vs. 2.08±0.94, TC (mmol/L): 1.39 (1.01, 2.23) vs. 2.69 (1.72, 3.81), all P < 0.01]. With the progression of the disease, the PCSK9 in the sepsis death group and the survival group was significantly lower than that within 1 day of diagnosis (all P < 0.05). ROC curve analysis showed that PCSK9 had higher predictive value of 28-day death than HDL-C, LDL-C, TC [area under ROC curve (AUC) and 95% confidence interval (95% CI): 0.748 (0.611-0.885) vs. 0.710 (0.552-0.868), 0.721 (0.575-0.867), 0.702 (0.550-0.854)]. Multivariate Logistic regression analysis showed that PCSK9 was an independent risk factor affecting the 28-day prognosis of sepsis (β value was 1.014, P = 0.020). Kaplan-Meier survival curve analysis showed that when PCSK9 ≥ 208.97 μg/L, with the increase of PCSK9, the 28-day survival rate of sepsis patients decreased significantly. Conclusions:PCSK9, HDL-C, LDL-C and TC can all predict the 28-day prognosis of patients with sepsis. The prognostic value of PCSK9 is the highest. PCSK9 is an independent risk factor affecting the prognosis of sepsis. In the early stage of the disease, PCSK9 may have a good predictive value for the prognosis of sepsis. When PCSK9 ≥ 208.97 μg/L, the 28-day survival rate decreased significantly.