Research

Urinary cystatin C is diagnostic of acute kidney injury and sepsis, and predicts mortality in the intensive care unit

Maryam Nejat¹, John W Pickering¹, Robert J Walker², Justin Westhuyzen¹, Geoffrey M Shaw^1,3, Christopher M Frampton¹ and Zoltán H Endre^1*

• * Corresponding author: Zoltán H Endre zoltan.endre@otago.ac.nz

Author Affiliations

¹ Christchurch Kidney Research Group, Department of Medicine, University of Otago Christchurch, Riccarton Avenue, Christchurch 8140, New Zealand

² Department of Medicine and Surgery, University of Otago, Leith Walk, Dunedin 9054, New Zealand

³ Intensive Care Unit, Christchurch Hospital, Riccarton Avenue, Christchurch 8140, New Zealand

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Critical Care 2010, 14:R85 doi:10.1186/cc9014

Published: 12 May 2010

Abstract

Introduction

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.

Trial registration

Australian New Zealand Clinical Trials Registry ACTRN012606000032550.