Abstract: Methods for detecting acute kidney injury in an individual comprise (a) contacting a body fluid sample from the individual with an assay device including neutrophil gelatinase-associated lipocalin (NGAL) antibody and a detectable label, to allow complexing of NGAL protein in the sample with NGAL antibody, and determining an amount of complex formed between NGAL protein from the sample and NGAL antibody in the assay device using the detectable label, wherein NGAL antibody in the device has binding capacity with more than two NGAL protein epitopes, and wherein the amount of the formed complex represents a level of acute kidney injury. Methods for determining an origin of NGAL protein in a sample from an individual include the step of determining relative amounts of monomeric, dimeric and heterodimeric forms of NGAL protein in the sample and allow improved diagnosis and therefore better targeted treatment.