In a study of 444 ICU patients, Nejat and colleagues prospectively studied the diagnostic and predictive performance of urinary cystatin C (uCysC) for AKI and 30-day ICU mortality. AKI was defined as a 50% or 0.3 mg/dL increase in plasma creatinine above baseline level. Eighteen percent of the patients had sepsis, 45% had AKI, and ICU mortality was 14%.