Diagnosis of acute kidney injury: from classic parameters to new biomarkers.

A change in serum creatinine is the standard metric used to define and monitor the progression of acute kidney injury (AKI). This marker is inadequate for a number of reasons including the fact that changes in serum creatinine are delayed in time after kidney injury and hence creatinine is not a good indicator to use in order to target therapy in a timely fashion. There is an urgent need for early biomarkers for the diagnosis of AKI. There is also a need for biomarkers that will be predictive of outcome and which can be used to monitor therapy. There are a limited number of biomarkers that are being validated by a number of groups and from this list clinically useful reagents are likely to be derived over the next few years. In this article the status of 5 potential urinary biomarkers for AKI are discussed: kidney injury molecule-1, N-acetyl-Beta-D-glucosaminidase, neutrophil gelatinase-associated lipocalin, cystatin C, and interleukin-18. Considerable progress has been made although much continues to be needed to validate these markers for routine clinical use. Armed with these new tools the future will look much brighter for the patient with AKI as it is likely that early diagnosis and better predictors of outcome will lead to new therapies which can be introduced earlier in the course of disease.