Monomeric neutrophil gelatinase associated lipocalin is associated with tubulointerstitial damage in chronic kidney disease

The rate of progression of chronic kidney disease (CKD) is difficult to predict using single measurements of serum creatinine or proteinuria. On the other hand, documented tubulointerstitial disease presages worsening CKD, but kidney biopsy is not practical for routine use and generally does not sample the tubulointerstitial compartment of the medulla. Perhaps a urine test that correlates with specific histological findings may serve as a surrogate for the kidney biopsy. Here we compared both immunoblot analysis (under non-reducing conditions) and a commercially available monomer immunoassays of Neutrophil Gelatinase Associated Lipocalin (NGAL) with pathological changes found in kidney biopsies, to determine whether specific histological characteristics associated with a specific NGAL species. We found that the urine of patients with advanced CKD contained NGAL monomers as well as higher molecular weight complexes containing NGAL, identified by MALDI-TOF/TOF mass spectroscopy. The NGAL monomer significantly correlated with glomerular filtration rate, interstitial fibrosis and tubular atrophy. Hence, specific assays of the NGAL monomer implicate histology associated with progressive, severe CKD.