Relationship of Red Cell Index with the Severity of Chronic Obstructive Pulmonary Disease

Abstract

Background

We aimed to investigate the association between red cell index (RCI) and the severity of Chronic Obstructive Pulmonary Disease (COPD), and compare predictive value of RCI, neutrophil–lymphocyte ratio (NLR) and platelet–lymphocyte ratio (PLR) for the severity of COPD.

Methods

A total of 207 participants were recruited (100 COPD patients and 107 healthy controls). COPD patients were divided into two groups according to the optimal cut-off value of RCI determined by the receiver operating characteristic (ROC) curve. Pearson’s correlation test, logistic regression analysis and other tests were performed.

Results

Compared with low RCI group, the forced expiration volume in 1 second (FEV₁) and FEV₁ in percent of the predicted value (FEV₁%) in high RCI group were lower (p = 0.016, p = 0.001). There was a negative correlation between RCI and FEV₁% (r = −0.302, p = 0.004), while no correlation between FEV₁% and NLR as well as PLR were found. RCI showed higher predictive value than NLR and PLR for predicting Global Initiative for Chronic Obstructive Lung Disease classification (GOLD), with a cut-off value of 1.75 and area under the curve (AUC) of 0.729 (p = 0.001). Multivariate logistic regression analysis proved that RCI was an independent factor for lung function in COPD patients (odds ratio [OR] = 4.27, 95% CI: 1.57–11.63, p = 0.004).

Conclusion

RCI is a novel biomarker that can better assess pulmonary function and severity of COPD than NLR and PLR. Higher RCI is related to deterioration of pulmonary function.

Keywords:

• COPD
• pulmonary function
• RCI
• biomarker

Abbreviations

COPD, chronic obstructive pulmonary disease; RCI, red cell index; NLR, neutrophil–lymphocyte ratio; PLR, platelet–lymphocyte ratio; Hb, Hemoglobin; Lym, Lymphocyte; PLT, Platelet; FEV₁%, forced expiratory volume in 1 second in percent of the predicted value; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; BODE, body mass index, airway obstruction, dyspnoea, exercise capacity; SGRQ, St. George’s Respiratory Questionnaire; GOLD, Global Initiative for Chronic Obstructive Lung Disease; ADO, age, dyspnea and airflow obstruction; DOSE, MRC Dyspnea Scale, airflow obstruction, smoking status and exacerbations; BMI, body mass index; PaCO₂, partial pressure of carbon dioxide in arterial blood; PaO₂, partial pressure of oxygen in arterial blood; ROC, receiver operating characteristics; AUC, the area under the curve.

Data Sharing Statement

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

Ethics Approval and Informed Consent

All participants provided written informed consent for participation in this study. The study was conducted in accordance with the ethical standards of the Ethics Committees of the Third Affiliated Hospital of Wenzhou Medical University (YJ20170015).

Acknowledgments

We thank all the participants in the study and the staff at the Third Affiliated Hospital of Wenzhou Medical University for their contribution in obtaining the data.

Author Contributions

Conceptualization: Xiaodiao Zhang, Meiying Cao; Methodology: Xiaodiao Zhang, Meiying Cao, Yiben Huang, Jianing Wang; Formal analysis: Jianing Wang, Jiamin Shen, Jiedong Ma, Xiaqi Miao; Investigation: Xiaodiao Zhang, Meiying Cao, Yiben Huang; Writing - original draft preparation: Yiben Huang, Jiang Wang, Jiamin Shen; Writing - review and editing: Xiaodiao Zhang, Meiying Cao; Methodology: Xiaodiao Zhang, Meiying Cao, Yiben Huang, Jianing Wang, Jiamin Shen, Jiedong Ma, Xiaqi Miao, Keke Ding, Bingqian Jiang, Binbin Hu, Fangyi Fu, Lingzhi Huang; Funding acquisition: Xiaodiao Zhang, Meiying Cao; Resources: Xiaodiao Zhang, Meiying Cao; Supervision: Xiaodiao Zhang, Meiying Cao. All authors made substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; took part in drafting the article or revising it critically for important intellectual content; agreed to submit to the current journal; gave final approval of the version to be published; and agree to be accountable for all aspects of the work.

Disclosure

The authors declare that they have no competing interests in this work.

Additional information

Funding

This work was funded by the Wenzhou Municipal Sci-Tech Bureau Program (grant number Y20180365). The Funding body had no role in the design of the study, data collection, interpretation of data, statistical analysis or the draft of the manuscript.