title: Immunoassays distinguishing between HNL/NGAL released in urine from kidney epithelial cells and neutrophils.
abstract: BACKGROUND
  The distinction between monomeric human neutrophil lipocalin/neutrophil gelatinase-associated lipocalin (HNL/NGAL), secreted by injured kidney tubular cells, and dimeric HNL/NGAL, released by activated neutrophils, is important to accurately diagnose acute kidney injury (AKI).
  
  
  METHODS
  132 urine samples from 44 intensive care unit (ICU) patients and five urine samples from non-ICU patients with urinary tract infections (UTIs) were analyzed by two monoclonal enzyme-linked immunosorbent assays (ELISA-1 and ELISA-2). The presence of monomeric and/or dimeric HNL/NGAL in each sample was visualized by Western blotting.
  
  
  RESULTS
  The ELISA-1 detected both monomeric and dimeric HNL/NGAL whereas the ELISA-2 almost exclusively detected dimeric HNL/NGAL with an area under the receiver-operating characteristics curve (AuROC) of 0.90. The ELISA-1/ELISA-2 ratio detected the monomeric form with an AuROC of 0.92. In 32 AKI patients, dimer-specific ELISA-2 levels decreased pre-AKI whereas the monomer-specific ELISA-1/ELISA-2 ratio gradually increased beyond AKI diagnosis. High ELISA-2 levels and/or low ELISA-1/ELISA-2 ratios detected a predominance of dimeric HNL/NGAL in urine from the patients with UTIs.
  
  
  CONCLUSIONS
  In combination, our two ELISAs distinguish monomeric HNL/NGAL, produced by the kidney epithelium, from dimeric HNL/NGAL, released by neutrophils during AKI development, as well as reduce the confounding effect of neutrophil involvement when bacteriuria is present.
authors.affiliation: Section of Anaesthesia and Intensive Care Medicine, Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden. johan.martensson@karolinska.se
authors.forename: Johan
authors.initials: J
authors.lastname: Mårtensson
authors.forename: Shengyuan
authors.initials: S
authors.lastname: Xu
authors.forename: Max
authors.initials: M
authors.lastname: Bell
authors.forename: Claes-Roland
authors.initials: CR
authors.lastname: Martling
authors.forename: Per
authors.initials: P
authors.lastname: Venge
mesh_terms: D058186:Acute Kidney Injury / Q000276:immunology / Q000473:pathology / Q000652:urine*; D000328:Adult; D000368:Aged; D001437:Bacteriuria / Q000276:immunology / Q000382:microbiology / Q000652:urine; D015153:Blotting, Western; D019281:Dimerization; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D004847:Epithelial Cells / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D007684:Kidney Tubules / Q000293:injuries / Q000378:metabolism* / Q000473:pathology; D054834:Lipocalins / Q000032:analysis* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D020033:Protein Isoforms / Q000032:analysis* / Q000378:metabolism; D014552:Urinary Tract Infections / Q000276:immunology / Q000382:microbiology / Q000652:urine
chemical_list: D054834:Lipocalins; D020033:Protein Isoforms