Table 4.

Novel blood and urine biomarkers being investigated for detection of cardiac surgery-associated AKI. NGAL, Neutrophil gelatinase-associated lipocalin. CysC, Cystatin C. IL-18, Interleukin-18. KIM-1, Kidney Injury Molecule-1. TIMP-2, tissue inhibitor of metalloproteinase. IGFBP7, insulin-like growth factor-binding protein. CCL-14, C-C motif chemokine ligand 14. AKI, acute kidney injury. CKD, chronic kidney disease.

Biomarker	Source	Pathophysiology	Utility in Cardiac Surgery	Limitations
NGAL	Blood, Urine	Upregulated in the proximal tubules after ischemic or nephrotoxic injury to the kidneys	Early detection of AKI	More specific in children and adults without CKD.
CysC	Blood	Functional biomarker with decreased clearance in AKI	Early detection of AKI Unaffected by differences in muscle mass.	Some studies have indicated that CysC has lower predictive value.
IL-18	Urine	Mediates ischemic and inflammatory kidney injury in the proximal tubules	Early detection of AKI	Some studies have indicated that IL-18 has lower predictive value.
KIM-1	Urine	Rapidly expressed in proximal tubular cells after ischemic kidney injury	Early detection of AKI	Some studies have indicated that it peaks up to 2–3 days after kidney injury.
[TIMP-2]*[IGFBP7]	Urine	Induces cell cycle arrest in renal tubular cells	Early detection of AKI Better sensitivity and specificity in predicting AKI.	Some studies have indicated that these biomarkers have lower specificity.
CCL-14	Urine	Mediates inflammatory kidney injury in the proximal tubules	Predicts persistent AKI and the need for RRT and can be used as a marker for progression of AKI to CKD	Does not provide early detection of AKI