Application of neutrophil-lymphocyte ratio and red blood cell distribution width in diabetes mellitus complicated with heart failure

Abstract

BACKGROUND

Accumulating clinical evidence has shown that diabetes mellitus (DM) is a serious risk factor for cardiovascular disorders and an important factor for adverse cardiovascular events.

AIM

To explore the value of the combined determination of the neutrophil-lymphocyte ratio (NLR) and red blood cell distribution width (RDW) in the early diagnosis and prognosis evaluation of DM complicated with heart failure (HF).

METHODS

We retrospectively analyzed clinical data on 65 patients with type 2 DM (T2DM) complicated with HF (research group, Res) and 60 concurrent patients with uncomplicated T2DM (control group, Con) diagnosed at Zhejiang Provincial People’s Hospital between January 2019 and December 2021. The NLR and RDW values were determined and comparatively analyzed, and their levels in T2DM + HF patients with different cardiac function grades were recorded. The receiver operating characteristic (ROC) curves were plotted to determine the NLR and RDW values (alone and in combination) for the early diagnosis of HF. The correlation between NLR and RDW with the presence or absence of cardiac events was also investigated.

RESULTS

Higher NLR and RDW levels were identified in the Res vs the Con groups (P < 0.05). The NLR and RDW increased gradually and synchronously with the deterioration of cardiac function in the Res group, with marked differences in their levels among patients with grade II, III, and IV HF (P < 0.05). ROC curve analysis revealed that NLR combined with RDW detection had an area under the curve of 0.915, a sensitivity of 76.9%, and a specificity of 100% for the early diagnosis of HF. Furthermore, HF patients with cardiac events showed higher NLR and RDW values compared with HF patients without cardiac events.

CONCLUSION

NLR and RDW were useful laboratory indicators for the early diagnosis of DM complicated with HF, and their joint detection was beneficial for improving diagnostic efficiency. Additionally, NLR and RDW values were directly proportional to patient outcomes.

Key Words: Neutrophil-lymphocyte ratio; Red blood cell distribution width; Type 2 diabetes; Heart failure; Early diagnosis

Core Tip: This study aimed to explore the value of the combined determination of the neutrophil-lymphocyte ratio and red blood cell distribution width in the early diagnosis and prognosis evaluation of diabetes mellitus complicated with heart failure.

INTRODUCTION

The continuous expansion of the aging population due to improved living standards has led to an increasing prevalence of various chronic diseases that have become serious public health issues, among which diabetes mellitus (DM) is of particular concern[1,2]. DM is an independent risk factor for cardiovascular disease (CVD)-the major cause of death in chronic complications of DM[3], and patients with DM have a twofold increased cardiovascular risk compared with non-DM patients[4]. Heart failure (HF), a common cardiovascular condition showing a rising prevalence, is the terminal stage of CVD. It affects over 26 million people worldwide and is a serious public health concern[5]. HF is a group of clinical syndromes caused by abnormalities in cardiac structure and/or function and ventricular systolic and/or diastolic dysfunction due to a variety of reasons, among which myocardial damage, abnormal cardiac load, and arrhythmia are the major causes[6,7]. Clinically, DM and HF often coexist and exacerbate each other. In the early stage of HF, DM patients may not present any obvious clinical symptoms, and abnormal cardiac structure and function are observed during an examination, whereas clinical symptoms of diastolic HF present in the middle and late stages[8]. The incidence of HF in DM patients is 9%-22%, which is significantly higher compared with that in non-DM patients[9]. However, the accuracy of a comprehensive diagnosis of HF based on symptoms and signs is limited because its clinical manifestations are nonspecific and not highly correlated with cardiac function or patient outcomes[10].

In recent years, domestic and foreign studies have newly uncovered the correlation of some markers in peripheral blood, such as the neutrophil-lymphocyte ratio (NLR) and red blood cell distribution width (RDW), with HF occurrence, development, and prognosis[11,12]. Neutrophil and lymphocyte counts are markers of inflammation severity[13]. Foreign studies have found that a low percentage of lymphocytes is an independent predictor of prognosis in in patients with acute coronary syndrome[14]. Evidence also shows that a relatively low percentage of lymphocytes is related to hospitalization and mortality rates in patients with acute HF (AHF)[15]. The NLR is an emerging marker of complex inflammatory response that combines two leukocyte subtypes (neutrophils and lymphocytes) and represents the activation of the inflammatory response (increased neutrophil count) and the immune stress response in the body (decreased lymphocyte count), with its ratio reflecting the relative balance between neutrophils and lymphocytes[16]. The RDW, which reflects erythrocyte volume heterogeneity, was initially used to distinguish anemia types and has now been revealed as a valuable prognostic indicator for CVD, particularly HF[17]. Increased RDW also reflects an underlying inflammatory state[18]. However, it is unclear whether NLR and RDW can be used as effective predictors of early HF, particularly in patients with diabetes. Therefore, this study explored the value of the combined detection of NLR and RDW in the early diagnosis and prognostic evaluation of DM complicated with HF.

MATERIALS AND METHODS

Study subjects

We retrospectively analyzed data on patients with type 2 DM (T2DM) complicated by HF who were diagnosed at Zhejiang Provincial People’s Hospital from January 2019 to December 2021. The study population included 65 T2DM patients complicated by HF (research group, Res) and 60 concurrent patients with uncomplicated T2DM (control group, Con). The inclusion criteria were as follows: (1) Diagnosis of chronic HF according to the diagnostic criteria of the Chinese Guidelines for the Diagnosis and Treatment of HF 2014, formulated by the Cardiovascular Branch of the Chinese Medical Association and confirmed diagnosis by clinical symptoms, signs, electrocardiography, chest X-ray, and echocardiography, with left ventricular ejection fraction (LVEF) < 50% by color Doppler echocardiography, New York Heart Association (NYHA) functional classification grade II-IV, as well as fatigue, palpitation, dyspnea, and edema of lower limbs after exercise; (2) diagnosis of DM according to the diagnostic criteria of the Chinese Guidelines for the Prevention and Treatment of Type 2 Diabetes (2017 edition), with fasting plasma glucose ≥ 7.0 mmol/L, 2-h postprandial blood glucose ≥ 11.1 mmol/L, and glycosylated hemoglobin ≥ 6.5%; (3) age ≥ 60 years; (4) HF duration > 12 months; and (5) complete clinicopathological and follow-up data. The exclusion criteria were: (1) Severe hepatorenal dysfunction; (2) malignant tumors; (3) HF caused by nondiabetic factors, such as hyperthyroidism, viruses, and rheumatic immune system diseases; (4) acute myocardial infarction within the past 6 months; (5) severe diabetic complications; (6) other diseases, such as severe malnutrition and abnormal liver function; and (7) severe arrhythmia, hypovolemia, hypokalemia, and recent infection.

Outcome measures and detection methods

General information, such as age, sex, body mass index (BMI), and the presence of basic diseases, were collected for each patient. NLR and RDW values were determined for comparative analysis. Fasting venous blood was drawn for each study subject and sent to the hospital laboratory, where routine hematological parameters, including RDW and lymphocyte count, were determined using a Sysmex XE-2100 automated blood cell analyzer and related reagents (Sysmex). The NLR value was calculated and recorded along with the RDW for comparative analysis. The laboratory reference ranges were as follows: RDW, 10.6%-15.0%; neutrophil count, 2.04-7.50 × 10⁹/L; lymphocyte count, 1.1-3.2 × 10⁹/L; and NLR: 1.85-2.34.

Statistical methods

The sample size was calculated using PASS v15.0 (NCSS Statistical Software, Kaysville, UT, United States). Data from a preliminary study showed that for a study power of 80% (α = 0.05, β = 0.2), assuming that the expected area under the receiver operating characteristic curve (AUC) of combined diagnosis was 0.90, the required sample size for each group was 52, with 104 patients necessary adequate for data collection, an expected 10% loss of follow-up, and at least 60 patients per group.

The data were processed and statistically analyzed using SPSS 25.0 software. Measurement data conforming to a normal distribution were described as the mean ± SD, t-tests were used for intergroup comparisons, one-way ANOVAs were used for multigroup comparisons, and least significant difference t-tests were employed for pairwise comparisons. Chi-square tests were performed to analyze count data expressed as percentages. The diagnostic efficacy of NLR and RDW in HF was analyzed using receiver operating characteristic (ROC) curves. P values < 0.05 were considered statistically significant.

RESULTS

General information

Intergroup comparisons of the general information between the Res and the Con groups showed that the sex, age, BMI, diabetes course, and presence of uncomplicated diseases were similar (P > 0.05; Table 1).

Table 1 Comparison of patients’ general data.

	Research (n = 65)	Control (n = 60)	t/χ2	P value	95%CI
Sex (male/female)	39/26	40/20	0.5962	0.4400	0.3610 to 1.5580
Average age (yr)	64.66 ± 5.45	66.63 ± 6.15	1.6132	0.1093	-0.3856 to 3.8370
BMI (kg/m2)	22.39 ± 1.75	22.91 ± 1.84	1.6193	0.7079	-0.1081 to 1.1630
Course of diabetes mellitus (yr)	10.58 ± 1.95	10.68 ± 2.74	0.2365	0.8135	-1.1820 to 2.2130
NYHA grading of cardiac function			125.03	< 0.0001
I	0	60
II	19	0
III	25	0
IV	21	0
History of hypertension	30	25	0.2550	0.6136	0.5911 to 2.4360
Smoking history	32	23	1.5041	0.2201	0.7651 to 3.181

NYHA: New York Heart Association.

NLR and RDW levels in the two groups

The Res group showed higher NLR and RDW levels and a worse LVEF compared with the Con group, with significant intergroup differences (P < 0.05; Table 2).

Table 2 Neutrophil-lymphocyte ratio and red blood cell distribution width levels in two groups.

	NLR	RDW	LVEF (%)
Research (n = 65)	5.40 ± 1.79	16.00 ± 1.63	41.85 ± 7.23
Control (n = 60)	2.99 ± 0.98	13.88 ± 1.08	58.07 ± 6.79
t	9.2283	8.4976	12.9016
P value	< 0.0001	< 0.0001	< 0.0001
95%CI	-2.921 to -1.889	-2.619 to -1.629	13.73 to 18.71

NLR: Neutrophil-lymphocyte ratio; RDW: Red blood cell distribution width; LVEF: Left ventricular ejection fraction.

General data of patients in the Res group with different cardiac function grades

There were no significant differences in the proportion of men, age, and diabetes course among patients with different cardiac function grades (P > 0.05). However, NLR and RDW gradually increased, and LVEF gradually decreased with an increase in HF grade, and these associations were statistically significant (P < 0.05; Table 3).

Table 3 Comparison of general data in research groups with different cardiac function grades.

NYHA classification	n	Male	Age (mean ± SD)	Course of diabetes mellitus	NLR	RDW	LEVF (%)
II	19	8	62.79 ± 4.83	10.77 ± 1.83	3.91 ± 1.64	14.72 ± 1.25	45.82 ± 6.14
III	25	16	65.84 ± 5.81	10.30 ± 1.96	5.55 ± 1.31	15.53 ± 1.04	42.75 ± 5.94
IV	21	15	65.71 ± 6.25	10.75 ± 2.11	6.56 ± 1.48	17.72 ± 0.93	37.20 ± 7.23
F		3.8452	1.8600	0.4070	16.4300	42.7900	9.3240
P value		0.1463	0.1643	0.6674	< 0.0001	< 0.0001	0.0003

NYHA: New York Heart Association; NLR: Neutrophil-lymphocyte ratio; RDW: Red blood cell distribution width; LVEF: Left ventricular ejection fraction.

Efficacy of NLR and RDW in the early diagnosis of HF

ROC curves were constructed to analyze the sensitivity and specificity of NLR and RDW in the early diagnosis of HF. The AUCs for the NLR and RDW were 0.864 and 0.859, the sensitivities were 75.4% and 76.9%, and the specificities were 90.0% and 86.7%, respectively, for the early diagnosis of HF. However, joint detection of NLR and RDW resulted in an AUC of 0.915 in the diagnosis of early HF, with a sensitivity of 76.9% and a specificity of 100% (Figure 1 and Table 4).

Figure 1 Receiver operating characteristic curve of neutrophil-lymphocyte ratio and red blood cell distribution width for early diagnosis of heart failure. ROC: Receiver operating characteristic; NLR: Neutrophil-lymphocyte ratio; RDW: Red blood cell distribution width.

Table 4 Diagnostic efficiency of neutrophil-lymphocyte ratio and red blood cell distribution width.

	AUC	SE	Specificity (%)	Sensitivity (%)	95%CI
NLR	0.864	0.033	90.0	75.4	0.799-0.929
RDW	0.859	0.034	86.7	76.9	0.793-0.925
Joint detection	0.915	0.027	100.0	76.9	0.863-0.968

NLR: Neutrophil-lymphocyte ratio; RDW: Red blood cell distribution width; AUC: The area under the receiver operating characteristic curve.

NLR and RDW levels in patients with or without cardiac events

All patients in the Res group underwent a 1-year follow-up. Among the 65 patients with DM complicated with HF, 19 developed cardiac events, and the remaining 46 did not. NLR and RDW values were higher in HF patients with heart events compared with HF patients without heart events (P < 0.05; Table 5).

Table 5 Comparison of neutrophil-lymphocyte ratio and red blood cell distribution width levels in patients with or without cardiac events.

	n	NLR	RDW
Without cardiac events	46	4.97 ± 1.66	15.70 ± 1.64
With cardiac events	19	6.45 ± .68	16.72 ± 1.42
t		3.2610	2.3540
P value		0.0018	0.0217

NLR: Neutrophil-lymphocyte ratio; RDW: Red blood cell distribution width.

DISCUSSION

HF is a serious complication of T2DM and a major prognostic factor of death[19]. The early diagnosis of T2DM patients with HF will help to guide clinicians in their choice of treatment plan, significantly improving patient prognosis. Currently, there are no markers capable of early diagnosis of HF in patients with T2DM. A high NLR has been reported as a better marker of cardiogenic death than neutrophil or lymphocyte counts. Thus, NLR is of high research value as an inflammatory indicator that completely reflects two important pathways[20]. An elevated RDW indicates increased mean erythrocyte volume or size, decreased deformability, and increased brittleness, which leads to increased blood viscosity, suggesting the presence of various types of anemia (e.g., hematopoietic or congenital erythrocyte abnormalities) that may lead to hypertension and CVD[21].

This study explored whether changes in NLR and RDW in patients with T2DM + HF could be used as predictive indicators for the early diagnosis of HF. We observed higher NLR and RDW values in patients with T2DM + HF compared with patients with uncomplicated T2DM. Additionally, the NLR and RDW in the Res group increased gradually and synchronously with the worsening of cardiac function among patients with grade II, III, and IV HF, and this was statistically significant (P < 0.05). NLR is an inflammatory marker combining two immune system modalities with better clinical value than either one alone. Neutrophils mediate active nonspecific inflammatory responses, whereas lymphocytes mediate physiological stress responses[22]. Neutrophils release various proteolytic enzymes that stimulate the heart and affect cardiac function. However, in HF, the production of serum lymphocytes is reduced due to neuroendocrine abnormalities. Thus, the higher the cardiac function grade, the higher the NLR value. The NLR indicates the balance between neutrophil and lymphocyte levels and is an indicator of systemic inflammation. A high NLR is an independent predictor of major adverse cardiac events and mortality in patients with acute myocardial infarction. The NLR has also been evaluated in patients with coronary artery disease and acute coronary syndrome. The RDW reflects erythrocyte volume heterogeneity, and its increase indicates a large difference in erythrocyte size (dyserythropoieses)[23]. Oh et al[24] analyzed the RDW values, N-terminal prohormone of brain natriuretic peptide (NT-proBNP) levels, and echocardiogram parameters of 100 patients with AHF. After adjusting for other risk factors, statistical analysis revealed that an elevated RDW indicated an increase in left ventricular filling pressure (LVFP) in patients with AHF. Because LVFP is of great significance in the clinical management of AHF, this suggests that RDW is related to AHF prognosis. A comparison of the results of ROC curve analysis of NLR combined with RDW with those of NLR or RDW alone for the early diagnosis of HF indicated that NLR combined with RDW had a higher diagnostic efficiency. Finally, the 1-year follow-up revealed that HF patients with cardiac events had higher NLR and RDW levels compared with HF patients with no cardiac events, indicating that NLR and RDW have a clear predictive value for poor prognosis. Uthamalingam et al[25] were the first to report that NLR better predicted the short- and long-term outcomes of patients with acute decompensated HF compared with the neutrophil count or lymphocyte count alone. Wang et al[26] conducted a meta-analysis of 5979 patients with HF, revealing that all-cause mortality was higher in patients with a high NLR than in patients with a low NLR (HR = 1.28, 95%CI: 1.14-1.43), supporting the role of NLR as a predictor of all-cause mortality in HF patients. The pathological process of HF involves chronic inflammation, during which inflammatory factors that inhibit erythrocyte maturation are secreted. This leads to the entry of immature erythrocytes into the bloodstream, thereby increasing erythrocyte size heterogeneity resulting in an increased RDW. Additionally, HF is often accompanied by gastrointestinal congestion along with disease progression. This reduces the absorption capacity of erythrocyte metabolites, increasing the RDW. The RDW is a stronger predictor of cardiac function in chronic HF than NT-proBNP levels and NYHA class, the currently recognized prognostic factors for congestive HF[27]. Huang et al[28] conducted a meta-analysis of 18288 HF patients from 17 studies and reached a similar conclusion, namely that changes in RDW during admission, discharge, and treatment can be used as a prognostic marker for HF patients. In our study, NLR and RDW were increased in patients with T2DM complicated by HF and cardiac events, and the combination of NLR and RDW was confirmed as more effective for the early diagnosis of T2DM complicated with HF than either of them alone.

This study has some limitations. First, this was a single-center study with a limited sample size, so our findings might not be representative of the general population. Second, this was a retrospective study and potentially confounded by selection bias. Therefore, future research should be undertaken across multiple regions and centers. Third, our study lacks detailed data to rule out the influence of other indicators, such as markers of glycolipid metabolism.

CONCLUSION

According to several clinical prospective and retrospective studies domestically and abroad[29,30], NLR and RDW are related to HF occurrence, development, prognosis, and severity. Moreover, these indicators are convenient and cheap to measure and can be rapidly detected using commercially available hematology analyzers, allowing their widespread application in clinical practice and providing a sound basis for early detection and intervention of HF, as well as the prediction of malignant arrhythmia events in hospitals. Overall, NLR and RDW can be used as laboratory indicators for the early diagnosis of DM complicated with HF, and their combined detection is beneficial for improving diagnostic efficiency. Additionally, higher NLR and RDW levels are associated with a worse prognosis.