Immunoassays distinguishing between HNL/NGAL released in urine from kidney epithelial cells and neutrophils

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 EUSA-2 levels decreased pre-AKI whereas the monomer-specific ELISA-1/ELISA-2 ratio gradually increased beyond AKI diagnosis. High EUSA-2 levels and/or low ELISA-1/ELISA-2 ratios detected a predominance of dimeric HNL/NGAL in urine from the patients with tills.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.

Xu, ShengyuanUppsala universitet,Biokemisk struktur och funktion(Swepub:uu)shengyuanxu (author)
Bell, MaxKarolinska Institutet (author)
Martling, Claes-RolandKarolinska Institutet (author)
Venge, PerUppsala universitet,Biokemisk struktur och funktion(Swepub:uu)pervenge (author)
Karolinska InstitutetBiokemisk struktur och funktion (creator_code:org_t)

By the author/editor: Martensson, Joha ...; Xu, Shengyuan; Bell, Max; Martling, Claes- ...; Venge, Per

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