Original Investigation
Pathogenesis and Treatment of Kidney Disease
Presurgical Serum Cystatin C and Risk of Acute Kidney Injury After Cardiac Surgery

https://doi.org/10.1053/j.ajkd.2011.03.015Get rights and content

Background

Acute kidney injury (AKI) after cardiac surgery is associated with poor outcomes, but is challenging to predict from information available before surgery.

Setting & Participants

The TRIBE-AKI (Translational Research Investigating Biomarker Endpoints in Acute Kidney Injury) Consortium enrolled 1,147 adults undergoing cardiac surgery at 6 hospitals from 2007-2009; participants were selected for high AKI risk.

Predictors

Presurgical values for cystatin C, creatinine, and creatinine-based estimated glomerular filtration rate (eGFR) were categorized into quintiles and grouped as “best” (quintiles 1-2), “intermediate” (quintiles 3-4), and “worst” (quintile 5) kidney function.

Outcomes

The primary outcome was AKI Network (AKIN) stage 1 or higher; ≥0.3 mg/dL or 50% increase in creatinine level.

Measurements

Analyses were adjusted for characteristics used clinically for presurgical risk stratification.

Results

Average age was 71 ± 10 years (mean ± standard deviation); serum creatinine, 1.1 ± 0.3 mg/dL; eGFR-Cr, 74 ± 9 mL/min/1.73 m2; and cystatin C, 0.9 ± 0.3 mg/L. 407 (36%) participants developed AKI during hospitalization. Adjusted odds ratios for intermediate and worst kidney function by cystatin C were 1.9 (95% CI, 1.4-2.7) and 4.8 (95% CI, 2.9-7.7) compared with 1.2 (95% CI, 0.9-1.7) and 1.8 (95% CI, 1.2-2.6) for creatinine and 1.0 (95% CI, 0.7-1.4) and 1.7 (95% CI, 1.1-2.3) for eGFR-Cr categories, respectively. After adjustment for clinical predictors, the C statistic to predict AKI was 0.70 without kidney markers, 0.69 with creatinine, and 0.72 with cystatin C. Cystatin C also substantially improved AKI risk classification compared with creatinine, based on a net reclassification index of 0.21 (P < 0.001).

Limitations

The ability of these kidney biomarkers to predict risk of dialysis-requiring AKI or death could not be assessed reliably in our study because of a small number of patients with either outcome.

Conclusions

Presurgical cystatin C is better than creatinine or creatinine-based eGFR at forecasting the risk of AKI after cardiac surgery.

Section snippets

Design and Setting

The TRIBE-AKI (Translational Research Investigating Biomarker Endpoints in Acute Kidney Injury) Study is an investigator-initiated study that was funded by the National Heart, Lung, and Blood Institute. The primary objective of this study is to investigate novel biomarkers for the early detection of AKI. A second aim of the study is to identify novel presurgical biomarkers for AKI, with cystatin C having been proposed as the leading candidate. We conducted a prospective cohort study of adults

Baseline Characteristics

Of 1,220 adults enrolled in this study, 73 did not have serum cystatin C results, leaving 1,147 with all 3 measurements of kidney function. Mean age was 71 ± 10 (standard deviation) years; 68% (n = 780) were men, and 93% (n = 1,072) were white. Of the surgical procedures, 48% (n = 551) were bypass only, 29% (n = 332) were valve only, and 30% (n = 263) were both; 80% of surgeries were elective and 13% were repeated operations. Presurgical kidney function levels were as follows: cystatin C, 0.93

Discussion

AKI is among the most morbid complications of cardiac surgery. Not only does AKI lead to higher in-hospital mortality risk, but it also predisposes to long-term mortality risk, even in persons who appear to recover from the AKI episode.18, 19 In this large multicenter prospective study, we compared the ability of presurgical measurement of serum cystatin C, an alternative marker of kidney filtration, with the clinical standard of serum creatinine to risk-stratify for postsurgical AKI. Although

Acknowledgements

Members of the TRIBE-AKI Consortium are Charles L. Edelstein, Michael Zappitelli, Catherine D. Krawczeski, Madhav Swaminathan, Cary S. Passik, Simon Li, and Michael Bennett.

Support: The research reported in this article was supported by the American Heart Association Clinical Development award and grant RO1HL-085757 from the National Heart, Lung, and Blood Institute. The study was also supported by Clinical Translational Science Award grant number UL1 RR024139 from the National Center for

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    Originally published online May 23, 2011.

    Because the Editor-in-Chief recused himself from consideration of this manuscript, the Deputy Editor (Daniel E. Weiner, MD, MS) served as Acting Editor-in-Chief. Details of the journal's procedures for potential editor conflicts are given in the Editorial Policies section of the AJKD website.

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