Serum cystatin C levels are less affected by non-renal factors, and have been demonstrated to be a more accurate early biomarker of GFR reduction compared with Scr.[21] It has been found that elevated serum cystatin C level is an independent predictor of CIN.[22] Neutrophil gelatinase-associated lipocalin (NGAL), a 25-kDa protein covalently bound to neutrophil gelatinase, has been recognized as the earliest biomarker of AKI for now. This evidence concerns the gene MMP2 and cervical squamous intraepithelial neoplasia.