Objective  To compare the concentrations of urinary calprotectin （CLP） in adults with acute kidney injury （AKI） and healthy people to explore the prognostic value of urinary calprotectin for adult AKI.

Methods  From December 2020 to November 2021, 50 AKI patients and 30 healthy people at health examination center were selected for detecting urinary Calprotectin, serum creatinine, blood urea nitrogen, urinary kidney injury molecule-1 （KIM-1）, serum albumin and hemoglobin in two groups. General data were recorded for comparing the differences of the above parameters between two groups. Then the above AKI patients were grouped after 90-day follow-ups. The patients on renal replacement therapy （RRT） were classified as dialysis group while those not on RRT as non-dialysis group; The patients dying after 90 days were assigned as death group while those surviving as survival group. The related parameters were compared. Receiver operating characteristic curve （ROC） curve and survival curve （product limit method） of AKI patients were plotted for evaluating the prognostic value of urinary calprotectin for adult AKI.

Results  Urinary Calprotectin （65.02 ± 33.75） μg/L vs （37.85 ± 17.33） μg/L, urinary KIM-1 （52.21 ± 30.91）ng/L vs （30.86 ± 15.38）ng/L, blood creatinine （538.62 ± 233.91） μmol/L vs （62.03 ± 14.27） μmol/L and blood urea nitrogen （BUN） （20.85 ± 9.38） mmol/L vs （5.26 ± 1.02） mmol/L were higher in AKI group than those in healthy control group. Serum creatinine （654.53 ± 218.68） μmol/L vs （478.91 ± 221.49） μmol/L, urinary Calprotectin （92.26 ± 29.26） μg/L vs （50.99 ± 26.82 μg/L and urinary KIM-1 （65.69 ± 40.76）ng/L vs （45.27 ± 22.04）ng/L were higher in dialysis group than those in non-dialysis group. The diagnostic threshold of urinary Calprotectin predicting RRT was 76.92 μg/L, area under receiver operating characteristic （ROC） curve was 0.850 and the sensitivity and specificity were 76.5% and 87.9% respectively. No significant differences existed in the levels of urinary Calprotectin, hemoglobin, urinary KIM-1, blood urea nitrogen, systolic blood pressure or diastolic blood pressure between death and survival groups. Area under ROC curve of urinary Calprotectin in predicting 90-day mortality was 0.564. The sensitivity and specificity were 76.5% and 87.9% respectively. No significant difference existed in 90-day mortality between dialysis and non-dialysis groups（P＞0.05）.

Conclusion  The level of urinary calprotectin is significantly higher in adult patients with acute renal injury than that in healthy controls. Urinary calprotectin offers some degree of accuracy in predicting RRT demand. However, it does not perform well in predicting 90-day mortality of AKI patients.