Neutrophil Gelatinase-Associated Lipocalin (NGAL) in Peritoneal Dialytic Effluent: Preliminary Results on the Comparison between Two Different Methods in Patients with and without Peritonitisis  
[PERSON]  
1 Department of Nephrology, Dialysis and Transplant, San Bordolo Hospital, 36100 Vicenza, Italy; [EMAIL_ADDRESS] (S.M.M.M. ); [EMAIL_ADDRESS] (T.T. ); [EMAIL_ADDRESS] (V.C. ); [PERSON]S] (M.D.C.); [EMAIL_ADDRESS] (F.K.M. ); [EMAIL_ADDRESS] (A.G.); [EMAIL_ADDRESS] (C.R. ); [EMAIL_ADDRESS] (M.Z.) [PERSON]  
6 IAP, Universite de Paris-Sud, CNRS-PUB, Paris-Sud, France;  
It is associated with the lipocalin superfamily, a group of proteins implicated in the organism's defense against pathogens. Precisely, NGAL induces the activation of the innate immunity in the course of bacterial infection, furthermore, it modulates several eukaryotic cellular reactions and proliferation and differentiation processes [2]. In the kidney, NGAL is synthesized in the distal nephron and released into the urine from the ascending limb of the loop of Henle to the collecting ducts [4]. NGAL is a small sized molecule, is openly filtered, and is simply detected in blood, urine, and peritoneal effluent. Different studies have demonstrated its efficacy in the diagnosis of acute kidney disease (AKI) [5]. Currently, urine NGAL concentration is a valid and effective tool to detect renal tubular injury [6]. During bacterial infection, the pathogen and host compete for iron. In this context, NGAL binds bacterial siderophores blocking iron shuttling, thereby limiting bacterial growth [2]. These inflammatory features underline why NGAL levels have been found in the presence of infection, inflammatory statements, and kidney insult. Peritonitis (inflammation of the peritoneum membrane) is a frequent complication for peritoneal dialysis (PD) patients, and it is associated with catheter loss, shift to hemodialysis, temporary loss of ultrafiltration, potential membrane damage, and occasionally death. Despite progress in treatment and prevention, PD-associated peritonitis is still the main cause of morbidity and mortality in this population [7; 8]. In this context, several studies have reported significant increases in NGAL during peritonitis [7; 8]. In particular, our group demonstrated that peritoneal NGAL is poorly present in the peritoneal effluent of PD patients in a basal statement [8]. On the contrary, human peritoneal mesothelial cells can release NGAL during an inflammatory state [9]. Current clinical criteria for the diagnosis of peritonitis include clinical signs and symptoms, cloudy effluent, and positive culture [10]. However, these features may not always be suggestive in the timely identification of peritonitis. For this reason, various biomarkers have been tested for the early diagnosis of peritonitis. Therefore, as expected, peritoneal NGAL has been revealed to be a novel biomarker for the diagnosis of peritoneal dialysis (PD) associated peritonitis [11]. In particular, in a previous study, we confirmed that peritoneal NGAL is a great marker for the diagnosis of peritonitis, particularly combining with WBC in PDE (the gold standard for the diagnosis of peritonitis). In our PD Unit, for these reasons, peritoneal NGAL is employed as a biomarker of peritonitis, in combination with the traditional criteria based on the International Society of Peritoneal Dialysis (ISPD) guidelines [8; 9; 10; 11]. In Vicenza center, the quantitative evaluation of peritoneal NGAL is detected by a particle-enhanced turbidimetric immunoassay (BioPorto test) performed by the Clinical Chemistry and Hematology Laboratory at San Bortolo Hospital. Recently, a point-of-care test (POCT) for the rapid evaluation of NGAL based on semi-quantitative colorimetric test strips was introduced in our PD Unit. The POCT is currently accessible in the PD center at the bedside of the patient, and it is performed by qualified nurses, giving quick results.