Value of the neutrophil CD64 index for diagnosing secondary infection in severe acute pancreatitis patients

Objective: This study aimed to investigate the value of the neutrophil CD64 index for diagnosing secondary infection in Severe Acute Pancreatitis (SAP) patients. Methods: A total of 43 patients with SAP were enrolled between January 2011 and December 2015. Patient Acute Physiology and Chronic Health Evaluation II and Rason scores were calculated and blood samples were collected to determine the neutrophil CD64 index using flow cytometry. White blood cell counts and C-reactive protein levels were also determined for all patients. Blood culture (the gold standard for the diagnosis of infection subsequent to SAP) and other laboratory exams were done at the same time for the diagnosis of SAP. Receiver Operating Characteristic (ROC) curve analysis was performed to evaluate neutrophil CD64 as a biomarker of secondary infection in patients with SAP. Results: Twenty-seven SAP patients were diagnosed with secondary infection 7 to 14 d after admission. ROC curve analysis showed that at a neutrophil CD64 index of 3.52, secondary infection identification exhibited high sensitivity (85.2%) and specificity (87.5%), and Youden index was 0.727. Conclusions: The index of peripheral blood neutrophil CD64 is a highly sensitive marker for suspected secondary infection in SAP patients. Our study suggests that the neutrophil CD64 index could be a valuable marker for diagnosing infections subsequent to SAP.