Association of red blood cell distribution width-platelet ratio with mortality after coronary artery bypass grafting

Abstract

Background: This study aims to explore the association between red blood cell distribution width-platelet ratio (RPR) and mortality in patients after coronary artery bypass grafting (CABG).

Methods: Data on patients who underwent CABG from January 1, 2021, to July 31, 2022, were retrospectively collected. The locally weighted scatter plot smoothing (Lowess) method was utilized to display the crude association between RPR and in-hospital mortality. The areas under the receiver operating characteristic curves (AUC) were used to assess the discrimination. The cut-off value (0.107) of RPR was calculated using the Youden index method. The primary outcome was in-hospital mortality.

Results: In total, 1,258 patients were included. The Lowess curve showed an approximate positive linear relationship between RPR and in-hospital mortality. In the multivariable logistic regression model, RPR was an independent risk factor (OR 1.493, 95% CI [1.119-1.992] per standard deviation (SD) increase, p = 0.006) for in-hospital mortality after CABG. RPR (AUC 0.716, 95% CI [0.617-0.814]) demonstrated greater discrimination than RDW (AUC 0.578, 95% CI [0.477-0.680], p = 0.002). The cut-off value (0.107) of RPR was calculated for further analysis, and groups were further divided into the high RPR group (≥ 0.107) and the low RPR group (< 0.107). In the multivariable logistic regression model, high RPR (≥ 0.107) correlated with elevated risks of in-hospital mortality (OR 6.097, 95% CI [2.308-16.104], p < 0.001) and one-year mortality (OR 6.395, 95% CI [2.610-15.666], p < 0.001) after adjusting for all included covariates. Subgroup analyses revealed that high RPR consistently had increased risks of in-hospital mortality and one-year mortality. Besides, patients with low RPR show better one-year survival than those with high RPR.

Conclusion: Preoperative high RPR could serve as an independent risk predictor for in-hospital mortality and one-year mortality, which can be utilized to assess the prognosis of patients and further provide guidance for the treatment in patients following CABG.

Keywords: Coronary artery bypass grafting; In-hospital mortality; Red blood cell distribution width-platelet ratio.

Figure 1. Association of red blood cell distribution width-platelet ratio and in-hospital mortality.

The crude association was displayed using the locally weighted scatter plot smoothing (Lowess) method. The shaded area represents the 95% confidence interval. Data were collected from individual human samples.

Figure 2. ROC curve analysis of selected risk factors to predict in-hospital mortality after CABG.

RPR and RDW were independent risk factors selected by the multivariable logistic regression analysis. The red curve represents the prediction of RPR for in-hospital mortality, and the green curve illustrates the prediction of RDW for in-hospital mortality. Abbreviations: CABG, coronary artery bypass grafting; ROC, receiver operating characteristic; RPR, red blood cell distribution width-platelet ratio; RDW, red blood cell distribution width.

Figure 3. The one-year cumulative survival probability for high and low RPR groups.

The Kaplan–Meier curve depicts the cumulative probability of one-year mortality between high and low RPR, and the log-rank test (p value < 0.0001) is used to compare the survival difference between the two groups. The blue curve indicates the survival of patients in the low RPR group, and the red curve illustrates the survival of patients in the high RPR group. The shaded area represents the 95% confidence interval. The number of patients at risk is given for each subgroup every three months. Abbreviations: RPR, red blood cell distribution width-platelet ratio.

Figure 4. The forest plot for the association of high RPR and in-hospital mortality in subgroups.

The forest plot shows odds ratios and 95% confidence intervals obtained from binary logistic regression analyses, illustrating the relationship between high RPR and in-hospital mortality in each subgroup. The median of continuous variables was utilized for the division of each subgroup. Abbreviations: BNP, B-type natriuretic peptide; CI, confidence interval; LVEF, left ventricular ejection fraction; MAP, mean arterial pressure; OR, odds ratio; RDW, red blood cell distribution width; RPR, red blood cell distribution width-platelet ratio.

Figure 5. The forest plot for the association of high RPR and one-year mortality in subgroups.

The forest plot shows odds ratios and 95% confidence intervals obtained from binary logistic regression analyses, illustrating the relationship between high RPR and one-year mortality in each subgroup. The median of continuous variables was utilized for the division of each subgroup. Abbreviations: BNP, B-type natriuretic peptide; CI, confidence interval; LVEF, left ventricular ejection fraction; MAP, mean arterial pressure; OR, odds ratio; RDW, red blood cell distribution width; RPR, red blood cell distribution width-platelet ratio.