Which biomarker serves as an early predictor of acute kidney injury?

• A. Neutrophil gelatinase associated lipocalin
• B. Cystatin C
• C. Procalcitonin
• D. BNP

Answer: (A)

Early detection of AKI depends on biomarkers that rise quickly after kidney injury, before the traditional marker of kidney function (creatinine) changes. Neutrophil gelatinase associated lipocalin fits this role best because it is produced in large amounts by damaged renal tubular cells and by activated neutrophils, then appears in blood and urine within just a few hours of injury. This rapid rise allows clinicians to identify AKI earlier and intervene sooner, potentially limiting progression.

Cystatin C reflects glomerular filtration rate and can be a sensitive marker, often increasing earlier than creatinine, but its rise is not as tightly tied to the immediate tubular injury that drives AKI onset as NGAL. Procalcitonin is a marker of systemic infection and inflammation, not specific to kidney injury, and BNP relates to cardiac wall stress and fluid status, not early renal injury. Therefore, NGAL stands out as an early predictor of AKI.