Study population and data extraction

The personal information and clinical data of all patients were extracted from the MIMIC-III database using the structured query language. All adult patients (≥ 18 years of age) with AP were recruited. Patients were excluded when more than 5% of their key data were missing. When the patient was repeatedly admitted to the ICU for AP, only data regarding the first admission was evaluated. All methods were carried out in accordance with relevant guidelines and regulations.

We extracted data on age, sex, comorbidities (diabetes, hypertension, coronary heart disease, and chronic obstructive pulmonary disease), admission time, survival status, initial severity scores after admission to the ICU (sequential organ failure assessment [SOFA] score⁹, systemic inflammatory response syndrome [SIRS] score¹⁰, and Oxford Acute Severity of Illness Score [OASIS]¹¹), white blood cell count, platelet count, creatinine concentration, and blood glucose level. For the white blood cell count, platelet count, and creatinine concentration, we extracted data for first measurement after admission to the ICU. The outcome of the study was in-hospital mortality, which was defined as death during hospital stay.

We extracted all blood glucose measurement values recorded after admission and included them based on the following criteria: (1) the timing of detection was within 120 h after admission; (2) the first test result after admission was used as the initial value of blood glucose level, and then the value was included once in 23–48 h; and (3) the glucose value was measured at least three times. Patients with blood glucose measurement values that did not meet the above criteria were excluded. The values of six blood glucose-related indicators were included in the study: initial glucose (Glucose_initial), maximum glucose (Glucose_max), minimum glucose (Glucose_min), mean glucose (Glucose_mean), glucose standard deviation (Glucose_SD), and glucose coefficient of variation (Glucose_CV). Accordingly, the Glucose_CV and Glucose_SD constituted glucose variability parameters, with the Glucose_CV being the ratio of the Glucose_SD to the mean.