Assessment of the Relationship Between Red Cell Distribution Width and Brucellosis: A Case-Controlled Study

Background: As a multisystem infectious disease, there is inammation, which causes an increase in brucellosis. The red cell distribution width (RDW) has been identied as markers of inammation. The present study aimed to investigate the predictive contribution value of RDW in the diagnosis of brucellosis. Methods: Medical records of 398 patients with brucellosis and 398 age-matched and gender-matched healthy controls in a single center from January 2017 to December 2019 were retrospectively reviewed. Results: The mean age of brucellosis patients was 47.1±12.9 years. The RDW levels were signicantly higher in brucellosis group when compared to the control group (p < 0.001); The RDW levels were markedly lower in brucellosis male patients (cid:0) 14.32±2.15% (cid:0) when compared to the brucellosis female patient (cid:0) s 15.41±3.13% (cid:0) (t= -9.56, p < 0.001). The biochemical markers of brucellosis patients included erythrocyte, hemoglobin, HCT, corpuscular volume, hemoglobin, hemoglobin concentration were all negatively correlated with RDW (r = −0.227, -0.383, -0.266, -0.253, -0.311 and -0.225, all p < 0.001). The values of hemoglobin (β coecient = -0.084, p < 0.001), ESR (β coecient = -0.020, p = 0.004) were signicantly and independently correlated with RDW. Receiver operating characteristic (ROC) curve analysis showed that the best cutoff point for RDW in the diagnosis of brucellosis was 13.45%, which evaluated brucellosis with a sensitivity of 64.1% and a specicity of 83.9%. The area under the ROC curve for RDW was calculated as 0.80 (95% CI 0.769–0.831, P<0.001). Conclusion: This study revealed that the RDW in diagnosing brucellosis had a higher sensitivity and specicity. RDW values may be useful complementary indirect markers for the diagnosis of brucellosis.


Introduction
Brucellosis is a common zoonotic infection worldwide, affecting more than 500 000 people each year. Its prevalence is more than 10/100 000 population in some endemic regions [1]. In China, brucellosis is common; the incidence of human brucellosis is estimated to vary from < 0.03 to > 160 individuals per 100000 population [2]. Although its true incidence in China remains largely unknown, it is thought that this increase results from improvements in diagnosis and increased reporting.
Brucellosis has been prevalent for several years in China, and human brucellosis was distributed in 25 of 32 provinces or autonomous regions of China, especially in Xinjiang region. Consequently, this disease is a high economic and public health problem for sufferers [3].
Clinical diagnosis can be challenging, particularly in the early stages of brucellosis, when clinical manifestations may be quite atypical or non-speci c. Different elements of history, laboratory, and examination ndings have varied predictive power in diagnosing brucellosis, and clinical evaluation exists, but brucellosis can be easily overlooked. The RDW is an objective measurement, which reveals the variability of circulating red blood cells. In the past several years, RDW has received the attention in the eld of in ammation in as much as it was associated with unfavorable clinical outcomes in patients with myocardial infarction, acute pancreatitis-associated lung injury, polycystic ovary syndrome, spontaneous echo contrast, and ankylosis spondylitis [4][5][6][7][8], however, few studies about brucellosis in literature have examined this subject before. According to the literature, it is not exactly clear what changes occur in RDW in brucellosis. In the present study, we aimed to seek whether RDW levels are related to diagnosis brucellosis.

Materials And Method
This is a case-controlled retrospective clinical study. Data were collected from patients' records archived in Xinjiang medical university a liated the rst hospital from January 2017 to December 2019. In this time frame, there was a record of 398 patients. We then included 398 age-matched and gender-matched healthy individuals. This study was performed in accordance with the principles of the declaration of Helsinki. It was reviewed and approved by an institutional review board exemption and a waiver for the requirement of the written informed consent. We collected patients' blood samples and clinical symptoms at the admission, and then we analyzed laboratory parameters. The diagnoses depended on the combination of medical history, brucella agglutination titer test, and the exclusion of other in ammatory diagnoses.
These hematological variables were measured and recorded in healthy individuals as well.

Inclusion Criteria
Brucellosis patients were based on the brucella serum agglutination test (≥ 1:160). All patients and healthy individuals' were no less than 18 years old. There were no other acute and chronic infections.
Patients were matched 1:1 by age and gender with healthy individuals who had the medical examination in our center.

Exclusion Criteria
Patients were excluded from the study if they were con rmed for severe cardiovascular disease, signi cant liver disease, neoplasms, autoimmune disorders, other chronic in ammatory conditions, and being immunocompromised. Patients were excluded from the study if they had been treated before we collected patients' blood samples. Further exclusion criteria were if the patient's blood data were not complete. Patients cannot be con rmed by any means, and had a history of surgery were excluded.

Statistical analysis
Statistical analysis was performed with SPSS17.00 statistical software. Continuous variables were shown as mean ± standard deviation, and categorical variables were presented as a percentage. The groups were compared using the t-test for continuous variables and chi-square test for categorical variables. Correlations between 2 continuous variables were evaluated with the Pearson test. A simple correlation test (Spearman's test) was used to observe the correlation between two variables. A multivariate linear regression analysis with stepwise selection of covariance was used to explore the correlation between RDW and other variables. All candidate variables were checked to see if their signi cance has been reduced below the speci c level. If a non-signi cant variable was found, it is removed from the analysis. In addition, receiver operating characteristics (ROC) curve analysis was used to measure the performance of RDW. A p-value of less than .05 was considered statistically signi cant.

Multivariate Linear Regression Analysis
According to a multivariate linear regression analysis, values of HGB (β coe cient = -0.084, p < 0.001), ESR (β coe cient = -0.020, p = 0.004) were signi cantly and independently correlated with RDW (Table 4).  Receiver operating characteristic curve analysis showed that the best cutoff point for RDW in the diagnosis of brucellosis was 13.45%, which evaluated brucellosis with a sensitivity of 64.1% and a speci city of 83.9%. The area under the ROC curve for RDW was calculated as 0.80 (95% CI 0.769-0.831, P < 0.001) (Fig. 1).

Discussion
The present study revealed that they were signi cantly higher in the RDW, ESR, CRP and signi cantly lower in NLR of brucellosis patients when compared to healthy individuals. Moreover, a bivariate and multivariate linear regression analysis demonstrated that RDW was correlated signi cantly with biochemical markers, indicating that the RDW was heavily associated with brucellosis patients. The ROC curve analysis showed that the RDW in the diagnosis of brucellosis has a higher sensitivity and speci city.
The onset of clinical brucellosis can be acute or insidious. Presenting complaints are often nonspeci c symptoms such as fever, nocturnal malodorous diaphoresis, arthralgia, headache, malaise, anorexia, and myalgia [9]. The untreated fever pattern may be intermittent or remittent. Hepatosplenomegaly and lymphadenopathy may be found as well as signs and symptoms associated with other infected organs. In this study, the most common symptoms were fever, followed by fatigue, anorexia, sweating, weight loss, arthralgia, nausea and vomiting, weakness, headache, abdominal pain, chest pain, myalgia, back pain, lumbago, diarrhea, abortion, and neck pain, respectively. The study by Galinska [9] et al. was similar to ours, and the survey by Olt [10] et al. was inconsistent with ours. The reason may be related to their small sample size.
A parameter with the ability to establish the diagnosis of brucellosis has always been a center of attention for physicians. Many different parameters have been examined or are under active investigation for that purpose [11][12][13][14][15]. As for RDW, it is a measure of heterogeneity in the size of circulating red blood cells. It is one of the standard complete blood count components. It has been previously observed that RDW levels have clinical outcomes in various pathologies such as coronary artery disease, pulmonary hypertension, diabetes mellitus, stroke, heart failure, pulmonary embolism, acute pancreatitis, bacteremia, rheumatoid arthritis, in ammatory bowel disease, colon cancer, and celiac disease [16][17][18][19][20][21].
Although there are a few studies about the hematologic effects of the brucellosis in literature [15,22,23], not precisely clear pathogenesis of alteration in RDW, which may be associated with morbidity in this disease, is still lacking. Our ndings showed that RDW levels were signi cantly higher in brucellosis group when compared to the control group. A study by Patel et al. [24] was similar to our results, and it was signi cantly higher in RDW and signi cantly lower in NLR levels of brucella epididymo-orchitis when compared to non-brucella epididymo-orchitis. The study by Tekin et al. [22] and the study by Küçükbayrak et al. [16] was similar to ours as well. However, Togan et al. [15] reported RDW level was not signi cantly higher in the acute brucellosis patients compared to that of the controls. This nding may be the result of greater RDW levels in chronic in ammatory diseases compared to that in acute conditions. Although the exact pathophysiological basis of the relationship is unclear, chronic in ammation, are proposed underlying factors in this topic [24]. In addition, our survey found that RDW levels were signi cantly higher in female patients when compared to male patients.
Some studies found that elevations in RDW levels are associated with impaired erythropoiesis or erythrocyte degradation [18,19]. In the current study, RDW levels were negatively correlated with RBC, HGB, HCT, MCV, MCH, MCHC of the biochemical markers with brucellosis patients. Lack of RBC subgroups occurs in parallel with the increase in RDW. Moreover, the neutrophil count decreases when lymphocyte count increases. RDW increases in in ammatory conditions, and this increase are considered as an indicator of systemic in ammation.
Elevated RDW are be related to increased in ammatory markers, such as ESR and CRP, and a strong correlation of RDW with in ammatory markers, ESR, and CRP value has also been found [25][26][27]. In a study by Lippi et al. [27], a graded association of RDW with hs-CRP and ESR was reported, independent of various confounding factors. In the current study, RDW levels were signi cantly and independently correlated with HGB, ESR values.
Few studies had analyzed RDW with in ammatory markers of disease by the ROC curve analysis [18,23].
In our current study, ROC curve analysis, RDW had an area under the curve of > 0.8, and the best cutoff point for RDW in the diagnosis of brucellosis was 13.45%, which evaluated brucellosis with a sensitivity of 64.1% and a speci city of 83.9%. A study by Patel et al. [24] was not similar to our results. The area under a curve, speci city was higher in the present study when compared to a study by Patel et al. The reason may be our large sample patients and the different populations.

Limitations
The major limit of the current study was the retrospective study that was considered. Single blood sampling was the other limitation of the course. For these reasons, new prospectively controlled and randomized trials with multiple blood, sampling must be performed to con rm our results. Despite that we have suggested that high RDW may be useful data for brucellosis patients.

Conclusion
The present study showed that RDW levels were higher in patients with brucellosis, and RDW in the diagnosis of brucellosis had a higher sensitivity and speci city. RDW can be useful complementary indirect markers for the diagnosis of brucellosis. There is still a need for further prospective, multicenter studies with a large sample size to fully clarify the issue. Ethical approval for the study was obtained from the ethical review committee for the rst a liated hospital of Xinjiang medical university, without the need for speci c consent from patients.

Consent for publication
We declare our consent to publication.

Availability of data and material
Our data and images support the usability of our articles.

Figure 1
Receiver operating characteristic curve analysis of red blood cell distribution width.