2 MATERIALS AND METHODS
The clinical and laboratory data of 151 consecutive inpatients aged over 60 years old who were tested by blood culture were retrospectively analyzed from October 2022 to June 2023 at our hospital. If the patient’s diagnosis at the time of admission or during hospitalization was sepsis or septic shock, they were included according to the Survival Sepsis Exercise Guidelines [6]. Subjects who received their first dose of antibiotics more than 24 hours before screening for inclusion in this investigation were excluded. Exclusion criteria included pregnant women, immune-compromised patients receiving radiation therapy or cytotoxic drugs, patients with AIDS, organ transplant patients, patients with inherited immunodeficiency diseases, patients with chronic kidney disease (baseline serum creatinine ≥2mg /dL) or chronic liver failure (Child-Pugh grade C), patients with bacterial endocarditis who require long-term treatment, and patients with conditions impacting hematologic indices, such as hematologic diseases, tumors, autoimmune diseases, and trauma. The study protocol was approved by the Medical Ethics Committee of Fuding Hospital (The ethnical approval number: Fuding Hospital 2022325).
Blood samples (2 ml) were drawn from the median elbow vein of patients before treatment, and EDTA was used for anticoagulation. The Japanese SYSMEX XE 2100 fully automated hematocrit analyzer and associated reagents were employed for testing complete blood cell counts. Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) were calculated based on the patient’s neutrophil count, lymphocyte count, and platelet count obtained from routine blood tests. The procedures were strictly adhered to, according to standard operating procedures (SOPs), and all tests were completed during in-house quality control.
Two sets of bilateral double vials were taken for blood culture, and aerobic and anaerobic cultures were performed simultaneously. Blood samples were obtained extracted from peripheral venous puncture of the patients, directly injected into Bactec vials, and incubated in a Bactec incubator (BD Diagnostics, Franklin Lakes, NJ, USA). Blood culture vials were incubated at 37˚C for 7 days. Positive cultures were Gram-stained and subcultured on solid media for subsequent analysis. Microbial identification using conventional techniques and API systems (bioMerieux, BacT/ALERT 3D, France).
A positive blood culture result from a single vial on one side was considered positive for bacteria. When coagulase negativestaphylococcus, Propionibacterium, Corynebacterium, etc. are isolated in blood culture, the same strain should be isolated unilaterally or repeatedly at the same time, otherwise it is considered as contaminated with colonizing bacteria of skin.
Data normality was evaluated using the Shapiro-Wilk test, with non-normally distributed measurements expressed as median and quartiles (P25-P75). Nonparametric tests were utilized for intergroup comparisons: the Mann-Whitney U test for two groups and the Kruskal-Wallis H test for multiple groups. Data that conformed to a normal distribution were reported as mean ± standard deviation, and the t-test was employed for mean comparisons between groups. Categorical variables were measured using chi-square test (χ 2) or exact Fisher’s tests, as appropriate, and were reported as count (%). Receiver operating characteristic (ROC) curve analyses were conducted for blood routine parameters. The area under the ROC curve (AUC) for blood routine parameters was calculated to determine the standard error and 95% confidence interval (95% CI). The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were calculated according to the ROC curves. Statistical processing was carried out using SPSS 22.0 statistical software (IBM SPSS, Armonk, NY, USA). A P - value of less than 0.05 was considered statistically significant.