Table 1.

Uses and limitations of conventional biomarkers

	Uses	Limitations
Creatinine	Glomerular filtration marker eGFR estimation Biomarker of acute and chronic reduced kidney function	Variability in generation rates across individuals Significant tubular secretion leading to overestimation of GFR Significant extra-renal elimination Tubular reabsorption in low urine flow states Increases late after AKI
Cystatin C	GFR estimation (plasma) Biomarker of proximal tubular dysfunction (urine) Biomarker of acute and chronic reduced kidney function	Increases late after AKI May increase in inflammatory states and where there is thyroid dysfunction independent of kidney function Urinary Cystatin C is altered in the presence of albuminuria
Albuminuria	Biomarker of glomerular filtration barrier dysfunction Biomarker of proximal tubular dysfunction Early biomarker of AKI Independent risk factor for cardiovascular and all-cause mortality and ESRD	24 hour collections unreliable Significant intra-individual variability in albumin/creatinine ratio over short time periods
Urine sediment examination	Biomarker of AKI Biomarker of glomerular disease Biomarker of tubulointerstitial disease	Poor interobserver agreement Lack of standardization of reporting of results Heavily dependent on experience of the reader Uncertain correlation with histopathology

Abbreviations: AKI, acute kidney injury; eGFR, estimated glomerular filtration rate ESRD, end-stage renal disease