<qa>  What is the name of the biomarker used for the early diagnosis of AKI?Biomarkers such as kidney injury molecule-1 KIM-1 and neutrophil gelatinase-associated lipocalin NGAL have been used for the early diagnosis of AKI, although with no definitive results. The investigators explored the association between plasma aging biomakers such as sklotho and contrast induced nephropathy in patients undergoing percutaneous coronary intervention PCI with contrast injection. 