Skip to main content

Authors’ response to letter “Prediction of acute kidney injury in intensive care unit patients”

The Original Article was published on 16 November 2018

We thank Dr. Guo and coworkers for their interest and comments [1] on our article [2]. We have provided responses to their comments. First, we agree that the patient severity of illness and level of organ failure upon admission to medical cardiac intensive care units (MCICUs) may be important predictors for the development of acute kidney injury (AKI). Hence, we evaluated the predictive ability of urinary liver-type fatty acid-binding protein (L-FABP) and serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) for AKI in the analytical model that included the Sequential Organ Failure Assessment (SOFA) score. In the multivariate logistic regression analysis, L-FABP, NT-proBNP, and the SOFA score were all independent predictors of AKI (Table 1). According to these findings, we speculate that a novel panel consisting of L-FABP, NT-proBNP, and the SOFA score may improve the accuracy for predicting AKI in patients treated in MCICUs. Furthermore, the addition of both L-FABP and NT-proBNP to a baseline model that included established risk factors and the SOFA score further enhanced the net reclassification and integrated discrimination improvement; this difference was greater than that obtained for either of the biomarkers and the baseline model alone (Table 2). Therefore, upon admission of patients to MCICUs, combining the measurements of the two independent predictors of AKI—L-FABP and NT-proBNP—may improve the accuracy for the early prediction of AKI beyond that achieved with either predictor alone.

Table 1 Multivariate logistic regression analyses for predictors of acute kidney injury
Table 2 Discrimination and reclassification of combination of L-FABP and NT-proBNP for acute kidney injury

Second, unfortunately, the serum creatinine (SCr) concentration used for the diagnosis of AKI in our study had not been corrected according to fluid balance because of the inconsistent data recorded. Adjustment of the SCr concentration was proposed according to the assumption that the SCr concentration may be diluted by positive fluid balance [3]. However, Shen et al. have suggested that a large proportion of the infused fluid eventually leaks into the third space instead of contributing to blood volume [4]. Therefore, the use of adjusted SCr might have overestimated the AKI incidence [4]. Further studies are needed to clarify this issue.

Finally, the C-index observed following the addition of both L-FABP and NT-proBNP showed the improvement beyond that of the baseline model alone (Table 2). On performing the calibration using the Hosmer–Lemeshow test, the model involving the addition of both L-FABP and NT-proBNP to the baseline model showed a good fit, whereas the model involving the addition of a single biomarker or the baseline model alone showed a poor fit.



Acute kidney injury


Liver-type fatty acid-binding protein


Medical cardiac intensive care units


N-terminal pro-B-type natriuretic peptide


Serum creatinine


Sequential Organ Failure Assessment


  1. Guo RJ, Xue FS, Shao LJ. Prediction of acute kidney injury in intensive care unit patients. Crit Care. 2018;22:304.

    Article  Google Scholar 

  2. Naruse H, Ishii J, Takahashi H, Kitagawa F, Nishimura H, Kawai H, et al. Predicting acute kidney injury using urinary liver-type fatty-acid binding protein and serum N-terminal pro-B-type natriuretic peptide levels in patients treated at medical cardiac intensive care units. Crit Care. 2018;22:197.

    Article  Google Scholar 

  3. Macedo E, Bouchard J, Soroko SH, Chertow GM, Himmelfarb J, Ikizler TA, et al. Program to Improve Care in Acute Renal Disease Study. Fluid accumulation, recognition and staging of acute kidney injury in critically-ill patients. Crit Care. 2010;14:R82.

    Article  Google Scholar 

  4. Shen Y, Zhang W. Assessing association between fluid balance and acute kidney injury after cardiac surgery. Reply J Crit Care. 2018;45:249–50.

    Article  Google Scholar 

Download references


Not applicable.


Not applicable.

Availability of data and materials

Not applicable.

Author information

Authors and Affiliations



HN drafted this manuscript. JI revised the manuscript. HT supported the statistical analysis. JI is the author responsible for this manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Junnichi Ishii.

Ethics declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Additional information

See related letter by Guo et al.,

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Naruse, H., Takahashi, H. & Ishii, J. Authors’ response to letter “Prediction of acute kidney injury in intensive care unit patients”. Crit Care 23, 58 (2019).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: