Materials and methods

Study design

This was a prospective observational study conducted in a hospital-based setting over a period of one year. Patients presenting with ACP were enrolled at admission and followed throughout their hospital stay. The design allowed for the systematic documentation of clinical, biochemical, and imaging parameters without altering routine management, thereby ensuring that the findings reflected real-world practice.

Study setting

The study took place at a tertiary care referral hospital in Assam, India, which serves as a major center for advanced gastroenterology and hepatology. Assam and the North-Eastern region carry a considerable burden of pancreatitis, with alcohol-related and idiopathic cases being particularly common. As a referral center, the hospital receives complex cases from surrounding districts, providing a diverse patient population that is suitable for evaluating ACP.

Patient recruitment

Patients were recruited consecutively to minimize selection bias. All individuals presenting with suspected ACP during the study period underwent eligibility screening, which included clinical evaluation, laboratory testing, and imaging confirmation. Written informed consent was obtained from each participant before enrollment. Patients meeting the inclusion criteria were followed prospectively until discharge or death. A flowchart was prepared to illustrate the recruitment process, including the number of patients screened, excluded, and analyzed, thereby ensuring transparency in patient selection.

ACP diagnostic criteria

AP was defined according to the Revised Atlanta criteria, requiring at least two of the following: characteristic abdominal pain, serum amylase or lipase activity greater than three times the upper limit of normal, and imaging findings consistent with AP. CP was diagnosed based on imaging evidence of pancreatic calcifications, ductal irregularities, or parenchymal atrophy. Operationally, ACP was defined as AP fulfilling the Revised Atlanta criteria in patients with imaging evidence of established CP. This definition ensured accurate classification of patients with established chronic pancreatic damage experiencing acute inflammatory exacerbations. The distinction was critical, as ACP differs from isolated AP in its clinical course, severity, and outcomes. Applying standardized diagnostic criteria reduced the risk of misclassification and enhanced comparability with existing literature.

Inclusion and exclusion criteria

Adults aged 18 years and above presenting with clinical features of AP and imaging evidence of CP were eligible for inclusion. Patients with alternative diagnoses such as gallbladder disease, malignancy, or non-pancreatic abdominal pathology were excluded. Those with incomplete imaging, refusal of consent, or prior enrollment in similar studies were also excluded. These criteria ensured a homogeneous study population and minimized potential confounding factors.

Clinical and laboratory assessment

Baseline demographic data, including age, sex, and socioeconomic background, were recorded. Clinical history focused on comorbidities such as diabetes, hypertension, and cardiovascular disease, as well as lifestyle factors, including alcohol consumption and smoking. Laboratory investigations included serum amylase and lipase, liver function tests, renal function tests, and complete blood counts. Imaging studies, primarily contrast-enhanced CT (CECT), were performed to assess pancreatic morphology, necrosis, and complications. These parameters provided a comprehensive clinical and biochemical profile for each patient, enabling correlation with PCT levels and outcomes.

Procalcitonin measurement

Serum PCT levels were measured using a quantitative immunoassay based on electrochemiluminescence (Roche Diagnostics, Indianapolis, IN). Samples were collected at admission and after 48 hours to capture dynamic changes. Calibration was performed according to the manufacturer’s instructions, and internal quality controls were run with each batch. The laboratory reference range for healthy individuals was < 0.05 ng/mL. All assays were conducted in the hospital’s central laboratory, ensuring standardized procedures and reproducibility.

Outcomes

The primary outcome was a composite endpoint comprising in-hospital mortality, ICU admission, and persistent organ failure lasting for more than 48 hours. Secondary outcomes included local complications such as pancreatic necrosis and pseudocyst formation, prolonged hospital stay beyond 14 days, and the need for surgical or endoscopic intervention. These outcomes were chosen to reflect both systemic and local disease severity, providing a comprehensive assessment of ACP progression.

Statistical analysis

Data were analyzed using SPSS Statistics version 25.0 (IBM Corp., Armonk, NY). Continuous variables were tested for normality using the Shapiro-Wilk test and expressed as mean ± standard deviation (SD) or median with interquartile range (IQR), as appropriate. Categorical variables were presented as frequencies and percentages. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive accuracy of PCT for adverse outcomes, with area under the curve (AUC) values reported. Logistic regression models were constructed to identify independent predictors of mortality and organ failure, adjusting for confounders such as age, comorbidities, and alcohol use. A p-value < 0.05 was considered statistically significant. This rigorous statistical approach ensured robust evaluation of PCT’s prognostic utility in ACP. A schematic representation of the methodology is provided in Figure 1.

Figure 1: Study methodologyACP: acute-on-chronic pancreatitis; WBC: white blood cells; PCT: procalcitonin; ICU: intensive care unit