The diagnosis of acute renal failure has been problematic, with a review showing 35 working definitions being used in the literature. This lack of clarity gave rise to the ADQI group creating the terminology of acute kidney injury (AKI). AKI has been used to give foundation to both the RIFLE and AKIN criteria, which have been shown to perform well in predicting critical care and hospital mortality. Their criteria are based on measuring increases of serum creatinine from baseline levels, and tallying this with weight-based urinary volumes. Problems with these techniques lie in having accurate baseline creatinine values, with the MDRD formula often proving inaccurate. Criticisms have also been levelled at using serum creatinine at all, given its variance with different body-mass compositions and fluid-balance status, as well as its relatively late rise in AKI compared to its utility in chronic renal failure.