Acute kidney injury. Rapid damage to cells of the kidney, resulting in loss of function. Acute kidney injury may be caused by nephrotoxic drugs, insufficient blood flow to the kidneys (resulting in ischemia) or other insults. It is functionally defined by the Acute Kidney Injury Network (an international interdisciplinary group of nephrologists and critical care physicians) as being characterized by a rapid time course (<48 h) and a reduction of kidney function, detected by either an increase in absolute serum creatinine (SCr) of ≥0.3 mg/dl (≥26.4 μmol/l) or a >50% increase in SCr, as well as a reduction in urine output to <0.5 ml/kg/h for >6 hours. The initial histomorphological changes in acute kidney injury may include changes in cell morphology or architecture (degeneration), including dilation and cell death (necrosis). Several days after the initial insult, tubular epithelial cells respond to epithelial cell loss and damage by regeneration or proliferation. Severe acute kidney injury or prolonged insults, termed chronic kidney injury, can result in progressive toxicity or typically a cascade of inflammation and fibrosis that irreversibly damages kidney integrity and function.
Area under the curve (AUC) for a ROC curve (see 'Receiver operating characteristic curve') is a metric to summarize the ability of a classifier to discriminate between two outcomes. As the name suggests, it can be calculated by integrating the receiver operating characteristic curve. It can be loosely interpreted as the sensitivity averaged across the levels of specificity.
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