Neutrophil-to-Lymphocyte Ratio Differentiates Infections from Sterile Inflammation in First Week of Acute Pancreatitis.

Background: Differentiating infections from sterile inflammation is crucial in early AP management.

Aim: This study aimed to assess the capability of Neutrophil-to-Lymphocyte Ratio (NLR) and procalcitonin to differentiate between sterile inflammation and infections in the first week of AP and to analyze the source, microbiological profile, and impact of infections in AP.

Methods: Consecutive patients presenting within 5 days of symptom onset were included. Microbiological profiles and serious adverse events (SAEs: in-hospital mortality or discharge in critical state) were analyzed. Blood count obtained at fever onset was used for calculating the NLR. The ability of NLR and procalcitonin to differentiate infections from sterile inflammation in the first week was assessed.

Results: Of 505 AP patients, 150 developed fevers. 48 (32%) had sterile inflammation, while 102 (68%) had infections. Most patients (n = 98, 65.3%) developed fever during the first week of illness (sterile inflammation (n = 43) and infections (n = 55)). NLR demonstrated good accuracy in differentiating infections from sterile inflammation in the first week (AUROC 0.70, p = 0.001), outperforming procalcitonin (AUROC 0.54, p = 0.58). Within infections (n = 102), 44 (43.1%) had infected pancreatic necrosis, 68 (66.7%) had extra-pancreatic infections, and 10 (9.8%) had both. Lower respiratory tract infection was the most common extra-pancreatic infection. Of 54 patients with culture-positive infections, 36 (66.7%) had grown multidrug-resistant (MDR) organisms. Fungal isolates were identified in 5 patients. Patients with infections had higher SAE incidence (21.6% vs. 4.2%, p = 0.007) than those with inflammation. The SAE incidence was higher with MDR infections than those without MDR (37.5% vs. 9.3%, p < 0.01).

Conclusions: Infections in AP occur early in the course of illness. NLR could serve as a reliable biomarker to distinguish infections from sterile inflammation in the early course of AP, aiding timely management. Patients with MDR infections have higher serious adverse outcomes.