Abstract
The neutrophil–to-lymphocyte ratio (NLR), as an essential systemic inflammation factor, has been widely used as a prognostic indicator in various diseases, such as malignant tumors, cardiovascular disease, and intracranial hemorrhage. An increasing number of studies have believed that NLR is a valuable predictor of prognosis for patients with aneurysmal subarachnoid hemorrhage (aSAH). However, these results remain controversial. In the current study, we planned to carry out a systematic review and meta-analysis to investigate the association between NLR and poor outcome, and the occurrence of delayed cerebral ischemia (DCI). We carried out a comprehensive search for published literatures on PubMed, EMBASE, Cochrane Library, and Web of Science databases from inception to April 1, 2021. We conducted an assessment of all included studies based on the principles proposed in the Newcastle-Ottawa Quality Assessment Scale (NOS). Poor outcome and the occurrence of DCI were considered as the main outcome measure. We calculated the pooled odds ratio (OR) and corresponding 95% confidence interval (CI) to examine the strength of the association of NLR with poor outcome or the occurrence of DCI. We strictly selected a total of 10 studies comprising 4,989 patients. Nine studies reported the association between NLR and poor outcome, and five studies reported the association between NLR and the occurrence of DCI. The pooled results indicated higher NLR was significantly associated with both poorer outcomes (OR = 1.32, 95%CI 1.11–1.57; P = 0.002, I2 = 87%), and the occurrence of DCI (OR = 1.72, 95%CI 1.22–2.41; P = 0.002, I2 = 82%) in aSAH patients. The NLR is a valuable indicator of inflammation to independently predict poor outcome and occurrence of DCI after aSAH, where a higher NLR is significantly associated with poor outcomes and occurrence of DCI. These findings suggest that the NLR can help clinicians evaluate the prognosis and identify potentially severe patients early, which may contribute to better management and improve poor prognosis of aSAH patients.
Highlights
Aneurysmal subarachnoid hemorrhage, results from a ruptured intracranial aneurysm, is a serious and life-threatening stroke subtype that can cause damage to the brain and it results in many neurologic disorders, with high mortality and morbidity, as well as severe burdens on the healthcare system [1,2,3]
The articles were required to satisfy the following inclusion criteria: [1] included adult patients (≥18 years of age) diagnosed with aSAH; [2] studies showing an association between neutrophil-to-lymphocyte ratio (NLR) and aSAH; and [3] the odds ratio (OR) and 95% confidence interval (CI) for efficacy outcome were provided from the multivariate analysis
The same analysis conducted on the basis of ethnicity showed that high NLR was significantly associated with poor outcome in Asian (OR = 1.42, 95%CI 1.08–1.87; P = 0.01), but not non-Asian samples (OR = 1.14, 95%CI 0.84–1.54; P = 0.40)
Summary
Aneurysmal subarachnoid hemorrhage (aSAH), results from a ruptured intracranial aneurysm, is a serious and life-threatening stroke subtype that can cause damage to the brain and it results in many neurologic disorders, with high mortality and morbidity, as well as severe burdens on the healthcare system [1,2,3]. Cerebral vasospasm or subsequent delayed cerebral ischemia (DCI) are common complications after SAH, which leads to poor neurological outcomes of SAH patients [5, 6]. There is growing evidence that systemic inflammatory reactions normally occur in the early stage of aSAH, cause damage to the hemorrhagic brain, and influence patients’ prognosis [9, 10]. Despite the exact mechanism still remains unclear so far, it is well-known that inflammation response plays a critical role in the progression of aSAH by initiating early brain damage, rebleeding, vasospasm, and subsequent DCI [10,11,12]. There has been a recent surge in research investigating the prognostic value of high NLR in prognosis of patients with aSAH. We systematically reviewed and performed a meta-analysis to quantitatively analyze the existing evidence and evaluate the prognostic value of NLR in aSAH patients
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