DOI: https://doi.org/10.21203/rs.2.11222/v2
Cerebral ischemic attack is a general term used for ischemic stroke, including cerebral thrombosis, embolism, and lacunar infarction. Seventy percent of cerebrovascular attacks are related to ischemic stroke, which is induced by a disorder in the brain–blood supply lesions. Ischemic stroke is the second most common cause of death, accounting for more than 20 million disabilities worldwide (1,2). However, tPA antithrombotic therapy, a recently introduced treatment for ischemic stroke, has had promising results (3,4).
A predictive parameter for stroke severity would enhance the antithrombotic therapeutic approach, which may reduce the high incidence and mortality rate of ischemic stroke (5,6). RDW is a hematologic parameter that indicates the divergence of red blood cell volume. Increases in RDW have been found in different physiological and pathological conditions such as pregnancy, vitamin B12 and folate deficiency, malignancy, idiopathic pulmonary fibrosis and coronary artery disease (7–12). Although RDW was created for the diagnosis of different types of anemia, recent research has revealed its predictive role in cerebrovascular diseases (13).
Different studies have shown an increased value of RDW after ischemic stroke (14–18). Feng et al. suggested that increased inflammation and oxidative stress during ischemia result in elevation in RDW and are associated with poor prognosis. However, it is still unclear that if RDW can predict the treatment response in stroke patients who are receiving antithrombotic therapy (16). Therefore, the present study aimed to investigate RDW’s ability to predict stroke severity and antithrombotic treatment outcomes in ischemic stroke patients. We hypothesized that RDW is a predictive marker for treatment response in patients receiving antithrombotic therapy.
This prospective study was conducted over 18 months, starting in April 2016. The participants were patients with definitive stroke diagnoses with specific criteria for tPA injection (19) who were admitted to the emergency department of Imam Reza University Hospital, Tabriz University of Medical Sciences. Those with transient ischemic attacks, intracerebral hemorrhage, cerebral sinus venous thrombosis, subarachnoid hemorrhage, renal insufficiency and pregnant women were excluded from the study population.
Blood samples were obtained at the time of admission to measure RDW. The patients completed follow-up examinations after three months. The severity of the stroke was assessed using the National Institute of Health Stroke Scale (NIHSS), and the clinical outcome was measured using the Modified Ranking Score (mRS) at 36 hours, 7 days, and 3 months.
RDW was calculated within 3 hours of admission using the Sysmex KX-21 automated cell counter (Sysmex Corporation, Kobe, Japan) and Ethylenediaminetetraacetic acid (EDTA). blood samples. RDW values of ≤12.9 were categorized as normal and values ≥13.0 were considered elevated. Stroke severity (NIHSS) was categorized as mild (0–6), moderate (7–15), and severe (16–38), and mRS <<2 (0,1, and 2) was defined as a fine outcome.
Statistical analysis was performed using SPSS software version 19.0 (IBM Corp., Armonk, NY, USA). The categorical variables were calculated as percentages, and the continuous variables were calculated as mean ± standard deviation. The continuous variables were compared using independent t-tests (for normally distributed data (20)), and the categorical variables were compared using qui-square tests. The ROC was performed to ensure the accuracy of RDW in detection of stroke severity, where an AUC close to 1 was considered to be a test with high predictive value. A multivariant linear regression analysis was conducted for correction of any other confounding factor (age, gender, hypertension, diabetes, hyperlipidemia, smoking, time of admission). A P-value < 0.05 was regarded as significant.
General Findings
Two-hundred eighty-two patients including 155 men and 127 women, aged 65.20 ± 12.70 years (17-90) were enrolled.
The mean NIHSS score was 13.16 ± 6.39 at time of admission, and it took averagely 55.99 ± 30.12 hours for tPA injection (5-184h). The NIHSS score improved significantly after the injection in 36 hours (p=0.027) with the mean thirty-six-hour score of 10.10 ± 8.93.
RDW values ranged from 10.4 to 20.5, with the mean value of 13.67 ± 1.17.
Mean values for RDW did not significantly correlate with the severity of stroke (p = 0.11). In mild form of stroke (NIHSS = 0-6), the mean value for RDW was 13.60 ± 0.22 and in stroke of moderate severity (NIHSS = 7-15), it was 13.58 ± 0.11. For patients with severe stroke (NIHSS > 16), the mean RDW was higher than the mild to moderate cases with mean value of 13.854 ± 0.12.
Table 1 demonstrates patients' characteristics according to the severity of stroke.
The patients were evaluated 7 days after the time of admission; however, the data was available only for 268 patients. The mean NIHSS was 2.7 ± 1.7 seven days after anti-thrombolytic therapy. The MRS was 3.14 ± 2.22 thirty-six hours after the treatment, which improved by 2.7 ± 1.73 in 7 days.
Classification of results based on the RDW values
The patients' characteristics according to the baseline RDW level is demonstrated in Table 2.
The categorization of RDW to <<12.9 and >13 values revealed insignificant difference in stroke severity score, accounting for the mean baseline NIHSS of 11.74 ± 6.39 in normal RDW values and 13.38 ± 0.49 in higher RDW group (p = 0.60). Similarly, the mean NIHSS of subjects with RDW<12.9 was lower than the patients with RDW>13 in each thirty-six-hour and seven-day evaluation, while the difference between two groups was statistically insignificant. The mean NIHSS was 8.19 ± 8.2 and 9.94 ± 8.28 in patients with normal and higher RDW values, respectively (p = 0.64). After seven days, NIHSS was 6.46 ± 7.28 in normal RDW group and was 8.52 ± 8.35 in increased RDW group (p = 0.058).
The categorization of final outcome according to RDW level demonstrated mean MRS of 2.74 ± 1.56 within thirty-six hours of tPA injection in the group of patients with normal RDW value, which was 3.25 ± 2.55 in increased RDW group. The final outcome results had a trend toward improvement in both RDW categories after seven days. The mean MRS was 2.33 ± 1.59 and 2.72 ± 1.75 in normal and increased RDW group, respectively.
Neither the thirty-six-hour, nor the seventh day MRS demonstrated significant difference between those with normal and higher RDW values.
The length of stay at hospital in patients with RDW<<12.9 was 14.34 ± 18.5 and in those with RDW > 13 was 15.08 ± 15.9. The results didn't differ significantly between two groups (p = 0.96).
SICH occurred in 14 patients, in 6 patients severe symptoms led to diagnosis and in 8 of them hemorrhage was asymptomatic. In patients with normal RDW level, 2.04% had symptomatic hemorrhage and 2.04% had asymptomatic hemorrhage. Among patients with elevated RDW, asymptomatic and symptomatic hemorrhage occurred in 4.69% and 3.35% of the patients. The analysis with Pearson's test did not reveal a correlation between SICH and RDW.
Three-month Follow up
Out of 282 enrolled subjects, only 208 referred for the three-month follow up session, 98 of them had a good final outcome with mean baseline RDW of 13.57 ± 1.35 and 110 had poor outcome on MRS evaluation with score of 13.76 ± 1.06. The linear regression analysis didn’t address any significant regression between final outcome results and baseline RDW values (r = 0.04, p = 0.52).
The sensitivity, specificity and AUC of baseline RDW for predicting final outcome within 36 hours were 77.6%, 69.8% and 0.51, respectively (Figure 1.A). In 7-day follow up, the sensitivity, specificity and AUC of baseline RDW were 75.0%, 74.3%, and 0.48, respectively (Figure 1.B). And during the period of 3 months the sensitivity, specificity and AUC of baseline RDW for MRS prediction were 74.4%, 71.4% and 0.57, respectively (Figure 1.C).
Corrections for confounding factors
Multivariant linear regression analysis revealed only a significant correlation between age and stroke severity (p= 0.01) and outcome (p= 0.03). However, after corrections for the age there was still an insignificant relation between RDW and stroke severity and outcome (p= 0.20).
In this prospective cohort study, the association between RDW and stroke severity and patients’ final outcomes was assessed to identify the possible predictive value of RDW in patients with stroke who underwent antithrombotic therapy with tPA. The results of the study revealed that stroke severity scores in subjects with baseline RDWs lower than 13 were lower than those with higher RDW values. Stroke severity improved after the injection of tPA, resulting in lower NIHSS results in each group after 36 hours and 7 days. However, the differences in stroke severity after 36 hours and 7 days post injection were not significant. The results of this study did not show a significant correlation between stroke severity and RDW values in patients who underwent tPA administration. In addition, RDW did not it did not predict the final outcome after 36 hours or 7 days. The results also revealed that the final outcome scale in a three-month interval follow upwas not correlated with the patients’ baseline RDW values. Therefore, RDW from an approximate AUC of 0.5 with a cut-off score of 13 did not appear to be predictive of final stroke outcome.
Kara et al. compared the RDW values in acute ischemic stroke patients in clusters with different severity scores and found that RDW played a significant role in the prediction of stroke severity (15). The authors also reported a significant correlation between RDW and other parameters, such as NIHSS and Glasgow comma score (GCS), and found that RDW with a cutoff point of 14, which was higher than the current study, had a high sensitivity and ability to differentiate stroke patients from normal subjects (AUC:0.76). In addition, Jia et al. studied 432 patients diagnosed with acute ischemic stroke and confirmed that RDW is closely related to the occurrence of ischemic stroke, revealing the importance of RDW in the progression of an ischemic stroke that may be related to carotid artery occlusion caused by large red blood cells (21).
In a population-based cohort study, Soderholm et al. (17) found that high RDW values revealed an increased risk of ischemic stroke. In the current study, the patients who underwent tPA injection had different findings than previous publications. In addition, Lappegård et al. found that elevated RDW levels cannot predict the risk of stroke-induced mortality after patients with anemia were excluded (22). However, Turcato et al. indicated that RDW may be used as an independent predictor of stroke severity and prognosis in patients with acute ischemic stroke who underwent antithrombotic therapy (23).
RDW is elevated in patients with ineffective erythropoiesis and may be associate with erythrocyte destruction. However, whether RDW is able to predict the incidence of stroke remains unclear. A population-based study with a normal control group may answer this question. RDW did not predict the severity of stroke and final outcomes in those who underwent tPA injection in the present study. However, this study only included patients with acute ischemic attack and excluded other types of stroke, severe cases (those with NIHSS>22), and those who were admitted more than 4.5 hours after symptom onset, which may explain the discrepancies in the findings of the current study and other studies in the literature. Moreover, while other studies proposed that inflammation was a predisposing factor in ischemia and may be related to elevated RDW levels (24,14), the results of this study did not confirm the association between RDW and ischemia. Further studies are required to resolve this issue.
Limitations
Our study had some limitations to be considered. The population of our study included some patients with other medical conditions, which may have a confounding impact on findings. It is better to add that with regards to the pathologic nature of ischemic stroke which target aged population, the exclusion of such comorbities was impossible. Moreover, only the patients with ischemic stroke who were admitted within sufficient time for tPA injection were included in the study. So, the results cannot be generalized to all forms of stroke patients or with admission severity score. However, the study population in this study were followed prospectively and any possible factor that could affect the outcome measure were considered. Thus, the results are sufficient enough to suggest RDW does not predict the severity and outcome of ischemic stroke in patients who undergo antithrombotic therapy.
Ethical approval and consent to participants
This study was approved by the regional ethical committee of Tabriz University of Medical Sciences (IR.TBZMED.REC.1395.344). A written informed consent was received from all the participants or their close relatives.
Acknowledgements
We appreciate the cooperation of the study subjects and technical staff at Department of Emergency Medicine in Imam Reza hospital. We also acknowledge Mr. Yousef Asgharzadeh and MRS. Zahra Seifar for their contribution in English editing of the paper.
Funding
The authors received no specific funding for this work.
Authors' contributions
KSh, ZhKh and ES contributed to study design and supervision, YGh, FH and FS contributed to the experimental evaluation, and analysis of data and writing of the manuscript. PM, MP and SM collected the data. All the authors read and approved the final manuscript.
Ethics approval and consent to participate
This study protocol was approved by the Ethical Committee of Tabriz University of Medical Sciences. All the participants were given written informed consent for the participation in this study.
Consent to publish
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Availability of data and material
The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.