Urinary cystatin C is diagnostic of acute kidney injury and sepsis, and predicts mortality in the intensive care unit.
BACKGROUND
To evaluate the utility of urinary cystatin C (uCysC) as a diagnostic marker of acute kidney injury (AKI) and sepsis, and predictor of mortality in critically ill patients.


METHODS
This was a two-center, prospective AKI observational study and post hoc sepsis subgroup analysis of 444 general intensive care unit (ICU) patients. uCysC and plasma creatinine were measured at entry to the ICU. AKI was defined as a 50% or 0.3-mg/dL increase in plasma creatinine above baseline. Sepsis was defined clinically. Mortality data were collected up to 30 days. The diagnostic and predictive performances of uCysC were assessed from the area under the receiver operator characteristic curve (AUC) and the odds ratio (OR). Multivariate logistic regression was used to adjust for covariates.


RESULTS
Eighty-one (18%) patients had sepsis, 198 (45%) had AKI, and 64 (14%) died within 30 days. AUCs for diagnosis by using uCysC were as follows: sepsis, 0.80, (95% confidence interval (CI), 0.74 to 0.87); AKI, 0.70 (CI, 0.64 to 0.75); and death within 30 days, 0.64 (CI, 0.56 to 0.72). After adjustment for covariates, uCysC remained independently associated with sepsis, AKI, and mortality with odds ratios (CI) of 3.43 (2.46 to 4.78), 1.49 (1.14 to 1.95), and 1.60 (1.16 to 2.21), respectively. Concentrations of uCysC were significantly higher in the presence of sepsis (P < 0.0001) or AKI (P < 0.0001). No interaction was found between sepsis and AKI on the uCysC concentrations (P = 0.53).


CONCLUSIONS
Urinary cystatin C was independently associated with AKI, sepsis, and death within 30 days.


BACKGROUND
Australian New Zealand Clinical Trials Registry ACTRN012606000032550.
Nejat
Maryam
M
Department of Medicine, University of Otago Christchurch, Riccarton Avenue, Christchurch 8140, New Zealand. maryam.nejat@otago.ac.nz
Pickering
John W
JW
Walker
Robert J
RJ
Westhuyzen
Justin
J
Shaw
Geoffrey M
GM
Frampton
Christopher M
CM
Endre
Zoltán H
ZH
D058186:Acute Kidney Injury / Q000401:mortality / Q000503:physiopathology / Q000652:urine*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D001315:Australia / Q000453:epidemiology; D003401:Creatine / Q000097:blood; D016638:Critical Illness / Q000401:mortality*; D055316:Cystatin C / Q000652:urine*; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011446:Prospective Studies; D018805:Sepsis / Q000401:mortality*
D055316:Cystatin C; D003401:Creatine
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