Association Between Red Blood Cell Distribution Width–Albumin Ratio and Hospital Mortality in Chronic Obstructive Pulmonary Disease Patients Admitted to the Intensive Care Unit: A Retrospective Study

Abstract

Purpose

High levels of red blood cell distribution width (RDW) and hypoalbuminemia are markers of poor prognosis in chronic obstructive pulmonary disease (COPD) patients. However, few studies have shown that the red blood cell distribution width–albumin ratio (RAR) is related to the mortality of COPD. This study aimed to explore the relationship between RAR and hospital mortality in COPD patients admitted to the intensive care unit (ICU).

Patients and Methods

Patients were retrospectively incorporated from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database and divided into two groups by a cutoff value of RAR. Propensity score matching (PSM) was performed to adjust for the imbalance of covariates. Logistic regression models and subgroup analyses were carried out to investigate the relationship between RAR and hospital mortality. The receiver operating characteristic (ROC) curve was used to evaluate the predictive performance of RAR and decision curve analysis (DCA) to assess the clinical utility.

Results

In total, 1174 patients were finally identified from the MIMIC-IV database. The cutoff value for RAR was 5.315%/g/dL. After PSM at a 1:1 ratio, 638 patients were included in the matched cohort. In the original and matched cohorts, the high RAR group had higher hospital mortality and longer hospital stays. Logistic regression analysis suggested that RAR was an independent risk factor for hospital mortality. The areas under the ROC curve in the original and matched cohorts were 0.706 and 0.611, respectively, which were larger than applying RDW alone (the original cohort: 0.600, the matched cohort: 0.514). The DCA indicated that RAR had a clinical utility.

Conclusion

A higher RAR (>5.315%/g/dL) was associated with hospital mortality in COPD patients admitted to ICU. As an easily available peripheral blood marker, RAR can predict hospital mortality in critically ill patients with COPD independently.

Graphical Abstract

Keywords:

• chronic obstructive pulmonary disease
• red blood cell distribution width
• albumin
• hospital mortality
• MIMIC-IV

Data Sharing Statement

The data incorporated in this study were obtained from the Medical Information Mart for Intensive Care IV (MIMIC-IV) Database (version 1.0), which was an open-access database and could be visited on the website after application: https://physionet.org/content/mimiciv/1.0/.

Ethics Approval and Informed Consent

This study was deemed exempt from review by the Ethics Committee of The First Affiliated Hospital of Xi’an Jiaotong University, and informed consent was not applicable given the nature of the retrospective study and the use of de-identified patient data extracted from public databases.

Consent for Publication

All authors have read this manuscript and consent to publish it.

Acknowledgments

This study was funded by the National Natural Science Foundation of China (Grant No. 81970050).

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis, and interpretation, or in all these areas; took part in drafting, revising, or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.