Rapid detection of acute kidney injury by plasma cystatin C in the intensive care unit.
BACKGROUND
Plasma cystatin C (pCysC) has been proposed as an alternative to plasma creatinine (pCr) as a measure of renal function. We compared the detection of functional change by both biomarkers in critically ill patients.


METHODS
pCysC and pCr were measured on admission to one of two intensive care units (ICU) and then daily over 7 days. Patients were classified according to the analyte that first increased by either ≥25 or ≥50% above the admission value. The proportion of patients in each class was compared using McNemar's chi-square test. Sustained acute kidney injury (AKI, a ≥50% increase in pCr from baseline for ≥24 h), dialysis and death within 30 days were recorded. The ability of pCysC and pCr on admission to predict sustained AKI, dialysis or death was assessed from the area under the receiver operator characteristic curve (AUC).


RESULTS
Of 442 patients, 83 had a ≥50% increase in one analyte, 17 in both and 342 in neither. Comparable numbers for a ≥25% increase were 163 in one analyte, 45 in both and 234 in neither. pCysC increased prior to pCr more frequently than vice versa in both the cohort with a ≥50% increase (P < 0.0001) and with a ≥25% increase (P < 0.0001). pCysC predicted sustained AKI with an AUC of 0.80 [95% confidence interval (CI) = 0.71-0.88]. pCysC and pCr were similarly moderately predictive of death or dialysis with AUCs of 0.61 [95% CI = 0.53-0.68] and 0.60 [95% CI = 0.51-0.67], respectively.


CONCLUSIONS
pCysC was an effective and earlier surrogate marker of decreased renal function than pCr in a general ICU population.
Nejat
Maryam
M
Christchurch Kidney Research Group, Department of Medicine, University of Otago, Christchurch, New Zealand.
Pickering
John W
JW
Walker
Robert J
RJ
Endre
Zoltán H
ZH
D058186:Acute Kidney Injury / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology; D000328:Adult; D000367:Age Factors; D000368:Aged; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged
C525030:CST3 protein, human; D055316:Cystatin C; D003404:Creatinine