Absolute blood eosinophil count could be a potential biomarker for predicting haemorrhagic transformation after intravenous thrombolysis for acute ischaemic stroke

BACKGROUND: Immune cells are involved in all stages of acute ischaemic stroke (AIS) and possess both neuroprotective and neurodamaging properties. It has been suggested that immune system activation after stroke may be associated with the development of haemorrhagic transformation (HT), which is the main complication limiting the clinical use of intravenous thrombolysis with recombinant tissue plasminogen activator (rtPA) for AIS. The purpose of our study was to analyse the association between absolute eosinophil count (AEC) at admission and the occurrence of HT after intravenous rtPA therapy for AIS. METHODS: In this retrospective study we enrolled AIS patients who were treated with rtPA within 4.5 h of symptom onset. Baseline stroke severity was evaluated using the National Institutes of Health Stroke Scale (NIHSS). Patients underwent head computed tomography scans at admission which were repeated 24 h after treatment with rtPA or promptly in case of clinical deterioration. HT was defined as blood at any site in the brain on follow-up head computed tomography scans. Spearman’s rank correlation test was used to analyse the correlation between AEC and NIHSS scores. The optimal AEC cut-off value for predicting HT was calculated using the area under the receiver operating characteristic curve. Multiple logistic regression was used to determine the association between AEC included as a binary variable and the incidence of HT. RESULTS: The data of 201 patients was analysed (59.7% females; median age 77 years); 23 (11.4%) of them developed HT. The median of AEC was 62.5% greater in the non-HT group compared to the HT group (0.13 × 10(9)/l and 0.08 × 10(9)/l, respectively, p = 0.026). No correlation was found between AEC and baseline NIHSS scores (r = 0.061, p = 0.393). AEC ≥ 0.11 × 10(9)/l predicted the occurrence of HT with 69.6% sensitivity and 60.7% specificity. AEC ≥ 0.11 × 10(9)/l was independently associated with a 78% reduction in the odds of developing HT (adjusted odds ratio = 0.223, 95% confidence interval = 0.069–0.723, p = 0.012). CONCLUSION: Higher values of AEC were associated with lower odds of developing HT, thus, AEC at admission could be considered an independent predictive marker of HT after treatment with rtPA for AIS.