title: Neutrophil gelatinase-associated lipocalin and acute kidney injury after cardiac surgery: the effect of baseline renal function on diagnostic performance.
abstract: OBJECTIVE
  Neutrophil gelatinase-associated lipocalin (NGAL) is rapidly released by renal tubules after injury, potentially allowing early identification of acute kidney injury (AKI) after cardiac surgery. However, the diagnostic performance of NGAL has varied widely in clinical studies, and it remains unknown what factors modify the relationship between NGAL and AKI. We hypothesized the relationship between urinary NGAL and AKI would vary with baseline renal function, allowing a stratified analysis to improve diagnostic performance of this novel biomarker.
  
  
  METHODS
  We performed a prospective observational study in 426 adult cardiac surgical patients. Urinary NGAL was serially determined, commencing preoperatively and continuing 24 hours postoperatively. AKI was defined as increase in serum creatinine from baseline by either >50% or >0.3 mg/dl within 48 hours postoperatively. Patients were stratified by baseline estimated GFR (eGFR). NGAL levels were compared between patients with and without AKI and diagnostic characteristics determined according to baseline eGFR.
  
  
  RESULTS
  In patients with baseline eGFR >or=60 ml/min, urinary NGAL was higher at all postoperative time points in patients who developed AKI compared with those who did not. In patients with baseline eGFR <60 ml/min, urinary NGAL did not differ at any time between those who did and those who did not develop AKI. Postoperative NGAL best identified AKI in patients with baseline eGFR 90 to 120 ml/min.
  
  
  CONCLUSIONS
  The relationship between urinary NGAL and AKI after cardiac surgery varies with baseline renal function, with optimal discriminatory performance in patients with normal preoperative function.
authors.affiliation: Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, PH-5, Suite 523, New York, New York 10032, USA. dm2655@columbia.edu
authors.forename: David R
authors.initials: DR
authors.lastname: McIlroy
authors.forename: Gebhard
authors.initials: G
authors.lastname: Wagener
authors.forename: H Thomas
authors.initials: HT
authors.lastname: Lee
mesh_terms: D000208:Acute Disease; D000209:Acute-Phase Proteins / Q000652:urine*; D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000652:urine; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D003404:Creatinine / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology / Q000652:urine; D000071068:Lipocalin-2; D054834:Lipocalins / Q000652:urine*; D008297:Male; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011518:Proto-Oncogene Proteins / Q000652:urine*; D013997:Time Factors; D015854:Up-Regulation; D055815:Young Adult
chemical_list: D000209:Acute-Phase Proteins; D015415:Biomarkers; C489506:LCN2 protein, human; D000071068:Lipocalin-2; D054834:Lipocalins; D011518:Proto-Oncogene Proteins; D003404:Creatinine