Circulating eNAMPT as a Diagnostic Biomarker in the Critically Ill: Acute Pancreatitis, Sepsis, Trauma, and Acute Respiratory Distress Syndrome

Abstract Background: Nicotinamide phosphoribosyltransferase (NAMPT) is a protein that exhibits dual functionality – as an intracellular enzyme which regulates nicotinamide adenine dinucleotide metabolism and as an extracellular protein (eNAMPT) secreted into the blood and functions as a cytokine regulator of innate immunity by activating NF-κB via binding to Toll-Like receptor 4. In limited preclinical and clinical studies, eNAMPT was implicated in the pathobiology of acute respiratory distress syndrome (ARDS) suggesting that eNAMPT could be a potential diagnostic and prognostic biomarker. Our aim was to investigate the feasibility of circulating eNAMPT levels to serve as a biomarker in an expanded cohort of patients with ARDS and ARDS-predisposing conditions such as acute pancreatitis, sepsis, and trauma when compared to controls. Methods: 795 patients and 179 healthy controls were included in the discovery and validation cohorts. Plasma and serum eNAMPT levels were quantified using one of two complementary Enzyme-linked Immunosorbent Assays. After log base 2 variance stabilizing transformation of plasma/serum eNAMPT measurements, differences between healthy controls and each disease cohort were compared using linear regression or generalized estimating equation (GEE) model where applicable. Complementary analyses included sensitivity, specificity, positive predictive values, negative predictive values, and the area under the receiver operating curve. Results: Compared to controls, circulating eNAMPT levels were significantly higher in patients with acute pancreatitis, with sepsis, with trauma, and with ARDS (all p<0.01). In the acute pancreatitis cohort, circulating eNAMPT levels positively correlated with disease severity (p<0.01). Conclusions: Circulating eNAMPT levels are a potential novel diagnostic biomarker in the critically ill with acute pancreatitis, sepsis, trauma, and/or ARDS.