Neutrophil-to-lymphocyte ratio is associated with increased cerebral blood flow velocity in acute bacterial meningitis

Abstract

In community-acquired bacterial meningitis (CABM) intracranial vascular alterations are devastating complications which are triggered by neuroinflammation and result in worse clinical outcome. The Neutrophil-to-Lymphocyte ratio (NLR) represents a reliable parameter of the inflammatory response. In this study we analyzed the association between NLR and elevated cerebral blood flow velocity (CBFv) in CABM-patients. This study included all (CABM)-patients admitted to a German tertiary center between 2006 and 2016. Patients' demographics, in-hospital measures, neuroradiological data and clinical outcome were retrieved from institutional databases. CBFv was assessed by transcranial doppler (TCD). Patients', radiological and laboratory characteristics were compared between patients with/without elevated CBFv. Multivariate-analysis investigated parameters independently associated with elevated CBFv. Receiver operating characteristic(ROC-)curve analysis was undertaken to identify the best cut-off for NLR to discriminate between increased CBFv. 108 patients with CABM were identified. 27.8% (30/108) showed elevated CBFv. Patients with elevated CBFv and normal CBFv, respectively had a worse clinical status on admission (Glasgow Coma Scale: 12 [9-14] vs. 14 [11-15]; p = 0.005) and required more often intensive care (30/30 [100.0%] vs. 63/78 [80.8%]; p = 0.01).The causative pathogen was S. pneumoniae in 70%. Patients with elevated CBFv developed more often cerebrovascular complications with delayed cerebral ischemia (DCI) within hospital stay (p = 0.031). A significantly higher admission-NLR was observed in patients with elevated CBFv (median [IQR]: elevated CBFv:24.0 [20.4-30.2] vs. normal CBFv:13.5 [8.4-19.5]; p < 0.001). Multivariate analysis, revealed NLR to be significantly associated with increased CBFv (Odds ratio [95%CI] 1.042 [1.003-1.084]; p = 0.036). ROC-analysis identified a NLR of 20.9 as best cut-off value to discriminate between elevated CBFv (AUC = 0.713, p < 0.0001, Youden's Index = 0.441;elevated CBFv: NLR ≥ 20.9 19/30[63.5%] vs. normal CBFv: NLR > 20.9 15/78[19.2%]; p < 0.001). Intracranial vascular complications are common among CABM-patients and are a risk factor for unfavorable outcome at discharge. Elevated NLR is independently associated with high CBFv and may be useful in predicting patients' prognosis.

Figure 1

Flowchart of patients. 141 patients with community-acquired bacterial meningitis were identified during the study period. After exclusion of 33 patients 108 patients remained for further analysis. Patients were dichotomized according to increased cerebral blood flow velocity (N = 30) and normal cerebral blood flow velocity (N = 78). Abbreviations: CABM community acquired bacterial meningitis, CBFv cerebral blood flow velocity, GOS Glasgow outcome scale (range, 5 no or mild deficit, to 1, death), NLR Neutrophil-to-Lymphocyte ratio.

Figure 2

Association of Neutrophil-to-Lymphocyte ratio (NLR) with increased cerebral blood flow velocity. Receiver operating characteristic (ROC)—curve for prediction of increased cerebral blood flow velocity. ROC plot demonstrated the AUC for increased cerebral blood flow velocity (AUC = 0.713; p < 0.001, Youden’s index = 0.441; sensitivity, 63.3%; specificity, 80.8%). The cut-off value was detected at 20.9.

Figure 3

Glasgow Outcome Scale at discharge with elevated CBF versus no elevated CBF. Illustration of the proportion of patients with elevated cerebral blood flow velocity (n = 30) and no/normal elevated cerebral blood flow velocity (n = 78). Favorable functional outcome was defined as GOS = 5, unfavorable functional outcome as GOS = 1–4. P values were calculated for the comparison of unfavorable functional outcome among patients elevated and normal CBFv (p = 0.01). Abbreviations: CBFv cerebral blood flow velocity, GOS Glasgow outcome scale (range, 5 no or mild deficit, to 1, death).