Elevated serum neutrophil gelatinase-associated lipocalin is an early predictor of severity and outcome in acute pancreatitis

Abstract

Objectives: About 210,000 new cases of acute pancreatitis (AP) involving reversible inflammation of the pancreas are reported in the United States every year. About one-fourth of all patients with AP go on to develop severe acute pancreatitis (SAP), which, unlike uncomplicated or mild acute pancreatitis (MAP, usually a self-limiting disease), constitutes a life-threatening condition with systemic complications, chiefly multiorgan dysfunction. An early prediction of the severity and outcome of patients with acute pancreatitis (AP) can lead to better treatment regimens for patients with SAP. There is currently no established biomarker for the early diagnosis of SAP. In this study, we investigated the potential of serum neutrophil gelatinase-associated lipocalin (NGAL) as an early marker to distinguish severe (SAP) from MAP and examine its ability to predict the prognosis of patients with SAP.

Methods: To check the time kinetics of rise in NGAL during AP, we quantified NGAL levels in sera from mice with MAP or SAP at various time points (6, 12, 24 and 48 h) using sandwich enzyme-linked immunosorbent assay. NGAL levels were also quantified in serum from 28 MAP and 16 SAP cases and compared with 28 chronic pancreatitis and 30 healthy control samples. Samples collected within 5 days from onset of symptoms were included. The relationship of NGAL levels with survival and multiorgan failure (MOF) in SAP was also examined.

Results: Although NGAL levels were significantly higher in mice with both MAP and SAP 6 h after induction (compared to control animals), only mice with SAP exhibited a significant increase in NGAL levels at 24 h (P=0.003). NGAL levels declined at 48 h after induction in animals with both MAP and SAP but did not reach baseline levels. Among patients, mean (+/-s.e.) serum NGAL level was significantly higher in SAP (634+/-139 ng/ml) compared to MAP (84.7+/-7 ng/ml, P=0.0001). On subanalysis, the difference between MAP and SAP cases was significant in the first 48 h but not at 72, 96, or 120 h. NGAL was 100%, 96%, 97%, and 84% specific and 100%, 87.5%, 92%, and 94% sensitive in distinguishing SAP from MAP at 48, 72, 96, and 120 h, respectively, after the onset of symptoms. NGAL levels were significantly higher in SAP cases complicated by MOF (P=0.004), and high NGAL levels in SAP appeared to correlate with a fatal outcome.

Conclusions: Our data provide the first evidence for the potential of serum NGAL as an early marker to distinguish MAP from SAP. Further, high NGAL levels predict MOF and fatal outcome in patients with SAP. This study provides sufficient evidence for multi-institutional randomized trials for estimating the potential of NGAL as early biomarker for SAP.

Figure 1

Mean (±s.e.) levels of NGAL/lipocalin-2 in sera of mice after the induction of acute pancreatitis. Sixty mice were randomized into three groups of 20 animals each. The mice were infused for 5 min with 4% sodium taurocholate (induces severe pancreatitis) or isotonic saline (induces mild edematous pancreatitis) into the CBD. Five mice from each treatment group were killed 6, 12, 24 and 48h after treatment and the serum samples were collected. Control mice injected with isotonic intraperitoneal saline do not develop any features of acute pancreatitis. The level of NGAL in the serum was quantified by enzyme-linked immunosorbent assay. (a) Mean serum NGAL levels (±s.e.) in mice with severe, mild, or no pancreatitis. NGAL levels were significantly higher in mice with severe pancreatitis compared to those with mild pancreatitis at 24 (P=0.003) and 48h (P=0.03) but not at 6 or 12h after induction. (b) Representative histology (H&E-stained sections) of the pancreas from control mice (left), mild pancreatitis (middle), and severe pancreatitis (right). Severe pancreatitis is characterized by marked inflammatory infiltration (arrows) and acinar cell necrosis (*), while these changes are rarely observed (necrosis) or significantly attenuated (inflammation). The duodenum is labeled as . Original magnification 1:25. CBD, common bile duct; H&E, hematoxylin and eosin; NGAL, neutrophil gelatinase-associated lipocalin.

Figure 2

Comparison of serum NGAL, CRP, Ranson’s score, peak APACHE-II score, and serum creatinine in patients with SAP with a fatal vs. nonfatal outcome. To examine the ability of serum NGAL levels to predict outcome, we compared NGAL levels in patients with SAP who died during the course of their illness with patients with SAP who survived. Cases were grouped according to the time the earliest serum sample was available after the onset of symptoms. Three patients with SAP who died during hospitalization were designated as case 1 (a), case 2 (b), and case 3 (c) (labeled as “dead” in the figure). For comparison, patients with SAP who had serum samples drawn at the same time point but who survived (labeled as “alive”) were chosen. Prognostic indicators, including plasma CRP, the Ranson’s score at 48h, the peak APACHE-II score, serum creatinine and serum NGAL levels, were compared between the two groups of patients (alive vs. dead). NGAL levels were markedly higher in the “dead” patients with SAP (9.2-, 5.3-, and 1.5-fold higher in cases 1, 2, and 3, respectively) compared to the mean NGAL level in the “alive” group. Patients with SAP who developed MOF are indicated by the asterisk (*) beside the patient number. NGAL concentrations in the graphs are 1/100th of the actual concentration for the respective patients. APACHE-II, Acute Physiology and Chronic Health Evaluation-II; CRP, C-reactive protein; MOF, multiorgan failure; NGAL, neutrophil gelatinase-associated lipocalin; SAP, severe acute pancreatitis.