Material and Method: We retrospectively analyzed 209 consecutive AIS patients and 202 age and sex matched healthy control subjects admitted to neurology clinics of Ankara Numune Training and Research Hospital and Ankara Training and Research Hospital between January and June 2014. Patients were classified into admission National Institute of Health Stroke Scale (NIHSS) score strata, and stroke subtypes were classified using Trial of Org 10172 in Acute Stroke Treatment (TOAST) and Bamford classifications. Mortality and functional outcome using modified Rankin Scale (mRS) was determined at 3 months.

Results: The mean age of patients was 68.5±13.9 years (106 men and 103 women). NLR was significantly higher in AIS group (4.00±3.76) compared to control group (2.18±0.99) (p <0,001). In patients with NIHSS≥16, NLR and mean platelet volume (MPV9) levels were significantly higher compared with moderate (6-15) and mild (≤5) NIHSS score group (p <0.001 and p =0.001, respectively). CRP levels were significantly higher in severe and moderate group (p <0.001). When patients are grouped according to functional outcomes at 3 months, NLR levels were significantly higher in patients who died (p =0.001) and CRP levels were significantly higher in patients who died and those with unfavorable outcome groups (p <0.001).

Conclusion: NLR may be used as a simple and easy-to-measure independent marker for prediction of mortality in acute ischemic stroke patients.

Patient Classification: Patients were classified according to stroke severity at admission using National Institutes of Health Stroke Scale (NIHSS) as mild (0-5), moderate (6-15), severe (≥16), Etiological subtypes were determined by Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification ⁹. Ischemic stroke was further subdivided according to the topographic of ischemic lesion on CT scan using Bamford classification as total anterior circulation stroke, partial anterior circulation syndrome, posterior circulation syndrome and lacunar syndrome ¹⁰. Functional outcome at 3 months was determined using modified Rankin Scale (mRS) and classified as favorable (mRS 0-2), unfa-vorable (mRS 3-5) and exitus (mRS 6).

Inclusion and Exclusion Criteria: Patients with a diagnosis of acute ischemic stroke on the first day of admission were included in the study. Exclusion criteria included patients who admitted to the hospital beyond 24 hours after AIS, patients with hematologic, inflammatory diseases, severe hepatic and renal insufficiency, immunosuppressant (steroids) or non-steroidal antiinflammatory drug users, those with an infection history within last 2 weeks, major cardiovascular disease history within 6 months (myocardial infarction, congestive heart failure) and patients with a history of malignancy. The study was approved by the local ethics committee.

Selection of Controls: The control group consists of the subjects that reported to the outpatient Neurology clinic of Ankara Numune Training and Research Hospital and Ankara Training and Research hospital between January and June 2014. Regardless of age, the controls had headache and vertigo as presenting complaint and were admitted to the inpatient care on Neurology floor.

Laboratory Tests: Complete blood count was performed using the peripheral venous blood samples acquired on admission to the emergency department. The blood sample was collected in a calcium ethylenedia-minetetra-acetic acid tube. Blood counts were estimated with an auto analyzer (Beckman Coulter, Fullerton, CA, USA). NLR was calculated as the ratio of neutrophils to lymphocytes in peripheral blood. Mean platelet volume (MPV) and red cell distribution width (RDW) values were also studied. The C-reactive protein (CRP) level was determined by the CRP assay (Bayer, Leverkusen, Germany), fibrinogen levels were measured using coagulometric method (Multifibren, Dode Behring/BCS, Marburg, Germany).

Statistical Analysis: Data were analyzed using SPSS software (version 22.0; SPSS Inc, Chicago, IL). Numerical variables were presented as mean±standard deviation or median (min-max) and categorical variables were presented as numbers with percentages. We determined the parametric test assumptions (normality and homogeneity of variances) for numerical variables using Shapiro Wilks test. The variances of the compared groups were analyzed using Levene test. When parametric test assumptions were met, t test was used and when parametric assumptions were not met, Mann Whitney U test was used for analysis. For the comparison of more than two groups, Kruskal Wallis test was used if parametric test assumptions were not met. Binary comparisons were made using Siegel Castellan test. The difference between groups in terms of categorical variables was determined using the Chi-square test. P value<0.05 was considered as significant.

Click Here to Zoom

Table 1: Clinical and demographic characteristics acute ischemic stroke patients and controls

NLR levels were significantly higher in AIS group (4.00±3.76) compared to control group (2.18 ± 0.99) (p <0.001). There was no statistically significant difference between men (3.73±3.30) and women (4.26±4.16) in the AIS group in regards to NLR (p=0.474).

In patients with NIHSS≥16, NLR and MPV levels were significantly higher compared to patients with NIHSS 6-16 and those with NIHSS≤5 (p<0.001 and p=0.001, respectively). CRP levels were significantly higher in patients with NIHSS≥16 and those with NIHSS 6-16 (p<0.001) (Table 2).

Click Here to Zoom

Table 2: Comparison of NIHSS scores with NLR and other laboratory parameters.

Among subtypes of TOAST classification, NLR was significantly higher among patients with cardio embolic ischemic stroke (4.99±4.17) compared with those with lacunar infarction (3.47±4.15) (p=0.010). MPV was significantly higher in patients with stroke of other determined etiology and stroke of undetermined etiology group compared to large artery atherosclerosis and lacunar groups (9.6±1.3 and 8.6±1 and 8.3 ± 0.9, respectively, p<0.001). CRP, RDW and fibrinogen levels were not significantly different between groups stratified according to etiologic subtypes.

When patients are analyzed in regards to Bamford classification, NLR and CRP were significantly higher in total anterior circulation compared to other groups (p=0.001), RDW, MPV and fibrinogen levels were not significantly different between groups.

NLR levels were significantly higher exitus group, which was significantly different than other groups. CRP levels, exitus and unfavorable outcome groups were significantly different than favorable outcome group. High NLR has also predicted the 3 months’ mortality in AIS patients (Table 3).

Click Here to Zoom

Table 3: Comparison of mRS scores with NLR and other laboratory parameters.

Studies in stroke patients are limited in the literature. Celikbilek et al ^7, demonstrated a significant increase of NLR in 70 AIS patients (p<0.001). NLR increase was significant in exitus patients (p=0.029). In another study by Tokgoz et al ^5, NLR has been shown to be a predictor of short term mortality in acute stroke patients in this study, when NLR is higher than 5, for short term mortality sensitivity was 83.1% and specificity was 62%. There was a strong correlation between NLR and NIHSS score. In another study, mean NLR was significantly higher in 126 acute ischemic stroke patients with nonvalvular atrial fibrillation ⁹.

It is known that inflammatory process develops within 6-24 hours of ischemic stroke and as a response to ischemic brain injury; neutrophils migrate to the damaged area resulting in accumulation in the ischemic brain tissue. Baseline neutrophil count is reported to increase the severity of ischemic damage and can cause poor neurologic outcome ¹⁸. On the other hand, lymphocytes began to increase 1 day after the stroke and peaks in the seventh day and particularly the effect of T cell lymphocytes is reported to have repair effects on inflammation ¹⁹. Higher neutrophil counts together with lower lymphocyte counts resulting with high NLR mean large damaged area with less repair effects resulting with poor outcome. Our study has also shown significantly higher NLR in non-survived patients. In the last decade, it is indicated that neutrophilia and lymphopenia are related independently with increased cardiovascular risk. Especially the maximum NLR ratio is stated to be a predictor factor on mortality in myocardial infarction ^11,20. In our study, NLR levels increased significantly in total anterior circulation strokes where the infarct volume is higher compared to other groups. High NLR has also predicted the 3 months’ mortality in AIS patients. NLR calculation which is an easy method to be performed at admission using the routine complete blood count can provide valuable information in addition to other clinical and radiological parameters such as NIHSS score and infarct volume. Also this study can be helpful to encourage experimental studies targeting the effects of inflammatory cells in terms of treatment of acute ischemic stroke as there are conflicting results concerning effects of neutrophils. In animal experiments, decrease of neutrophils has been shown to improve clinical course whereas there are some publications stating anti-neutrophil treatment is ineffective ^20-24. This was a retrospective and non-randomized single center study that included a relatively small number of patients. Therefore, the possibility of selection bias and/or residual confounding from unknown or unmeasured covariates cannot be excluded. Further studies with a larger sample size may be needed. NLR taken in the study was calculated from only complete blood count and consecutive counts taken may have more valuable correlations with stroke subtypes and functional outcomes.

These findings support the role of NLR as a simple, inexpensive and readily available marker of mortality in acute ischemic stroke. As NLR in acute ischemic stroke was studied in only few studies in the literature, the role of neutrophils and lymphocytes is still under debate and has to be explored in future clinical trials.

1) Ross R. Atherosclerosis an inflammatory disease. N Engl J Med 1999; 340: 115-26.

2) Libby P, Ridker PM, Maseri A. Inflammation and atherosclerosis. Circulation 2002; 105: 1135-43.

3) Horne BD, Anderson JL, John JM, et al. Which white blood cell subtypes predict increased cardiovascular risk? J Am Coll Cardiol 2005; 45: 1638-43.

4) Widmer A, Linka AZ, Attenhofer CH, et al. Mechanical complications after myocardial infarction reliably predicted using C-reactive protein levels and lymphocytopenia. Cardiology 2003; 99: 25-31.

5) Tokgoz S, Kayrak M, Akpinar Z, Seyithanoğlu A, Güney F, Yürüten B. Neutrophil lymphocyte ratio as a predictor of stroke. J Stroke Cerebrovasc Dis 2013; 22: 1169-74.

6) Arbel Y, Finkelstein A, Halkin A, et al. Neutrophil/lymphocyte ratio is related to the severity of coronary artery disease and clinical outcome in patients undergoing angiography. Atherosclerosis 2012; 225: 456-60.

7) Celikbilek A, Ismailogullari S, Zararsiz G. Neutrophil to lymphocyte ratio predicts poor prognosis in ischemic cerebrovascular disease. J Clin Lab Anal 2014; 28: 27-31.

8) Ertaş G, Sönmez O, Turfan M, et al. Neutrophil/lymphocyte ratio is associated with thromboembolic stroke in patients with non-valvular atrial fibrillation. J Neurol Sci 2013; 324: 49-52.

9) Adams HP Jr, Bendixen BH, Kappelle LJ, et al. Classification of subtype of acute ischemic stroke. Definitions for use in a multicenter clinical trial. TOAST. Trial of Org 10172 in Acute Stroke Treatment. Stroke 1993; 24: 35-41.

10) Bamford J, Sandercock P, Dennis M, Burn J, Warlow C. Classification and natural history of clinically identifiable subtypes of cerebral infarction. Lancet 1991; 33: 1521-6.

11) Kaptoge S, Di Angelantonio E, Lowe G, et al. C-reactive protein concentration and risk of coronary heart disease, stroke and mortality: an individual participant meta-analysis. Lancet 2010; 375: 132-40.

12) Zahorec R. Ratio of neutrophil to lymphocyte counts rapid and simple parameter of systemic inflammation and stress in critically ill. Bratisl Lek Listy 2001; 1: 5-14.

13) Pellizzon GG, Dixon SR, Gregg W, et al. Stent PAMI Investigators. Relation of admission white blood cell count to long-term outcomes after primary coronary angioplasty for acute myocardial infarction. Am J Cardiol 2003; 91: 729-31.

14) 14-Núñez J, Núñez E, Bodí V, et al. Usefulness of the neutrophil to lymphocyte ratio in predicting long-term mortality in ST segment elevation myocardial infarction. Am J Cardiol 2008; 101: 747-52.

15) Uthamalingam S, Patvardhan EA, Subramanian S, et al. Utility of the neutrophil to lymphocyte ratio in predicting long-term outcomes in acute decompensated heart failure. Am J Cardiol 2011; 107: 433-8.

16) Azab B, Zaher M, Weiserbs KF, et al. Usefulness of neutrophil to lymphocyte ratio in predicting short and long-term mortality after non ST-elevation myocardial infarction. Am J Cardiol 2010; 106: 470-6.

17) Tamhane UU, Aneja S, Montgomery D, Rogers EK, Eagle KA, Gurm HS. Association between admission neutrophil to lymphocyte ratio and outcomes in patients with acute coronary syndrome. Am J Cardiol 2008; 102: 653-7.

18) Tokgoz S, Keskin S, Kayrak M, Seyithanoglu A, Ogmegul A. Is neutrophil/lymphocyte ratio predict to short-term mortality in acute cerebral infarct independently from infarct volume? J Stroke Cerebrovasc Dis 2014; 23: 2163-8.

19) Schwartz M, Moalem G. Beneficial immune activity after CNS injury: prospects for vaccination. J Neuroimmunol 2001; 113: 185-92.

20) Duffy BK, Gurm HS, Rajagopal V, Gupta R, Ellis SG, Bhatt DL. Usefulness of an elevated neutrophil to lymphocyte ratio in predicting long-term mortality after percutaneous coronary intervention. Am J Cardiol 2006; 97: 993-6.

21) Grogaard B, Schurer L, Gerdin B, Arfors KE. Delayed hypoperfusion after incomplete forebrain ischemia in the rat. The role of polymorphonuclear leukocytes. J Cereb Blood Flow Metab 1989; 9: 500-05.

22) Easton AS. Neutrophils and stroke. Can neutrophils mitigate disease in the central nervous system? Int Immunopharmacol 2013; 17: 1218-25.

23) Krams M, Lees KR, Hacke W, Grieve AP, Orgogozo JM, Ford GA. Acute Stroke Therapy by Inhibition of Neutrophils (ASTIN): an adaptive dose-response study of UK-279,276 in acute ischemic stroke. Stroke 2003; 34: 2543-8.

24) Dirnagl U, Klehmet J, Braun JS, Gupta R, Ellis SG, Bhatt DL. Stroke-induced immuno-depression: experimental evidence and clinical relevance. Stroke 2007; 38: 770-3.