Pre-treatment levels of inflammatory biomarkers as predictors of reperfusion outcomes in acute ischemic stroke: a systematic review and meta-analysis

Title Pre-treatment levels of inflammatory biomarkers as predictors of reperfusion outcomes in acute ischemic stroke: a systematic review and meta-analysis 1. Research question and objectives Research question In patients with acute ischemic stroke treated with reperfusion therapies (intravenous thrombolysis and/or mechanical thrombectomy), are circulating inflammatory biomarkers measured prior to treatment associated with poor functional outcome? Objectives • To systematically identify studies assessing pre-treatment circulating inflammatory biomarkers in acute ischemic stroke patients undergoing reperfusion therapy • To evaluate the association between baseline inflammatory biomarkers and poor functional outcome, defined as modified Rankin Scale (mRS) score 3-6 • To perform meta-analyses for biomarkers with sufficient and comparable data • To descriptively summarize evidence for additional biomarkers and secondary outcomes, including mortality and hemorrhagic transformation 2. Eligibility criteria Population • Adult patients (≥18 years) • Acute ischemic stroke confirmed by neuroimaging • Patients treated with intravenous thrombolysis (IVT) and/or mechanical thrombectomy (MT) Exposure • Circulating inflammatory biomarkers measured in peripheral venous blood • Biomarker sampling performed prior to initiation of reperfusion therapy Outcomes • Primary outcome: poor functional outcome defined as mRS 3-6 • Preferred follow-up time point: 3 months (90 days) • Secondary outcomes: o Mortality o Intracerebral hemorrhage (ICH) o Symptomatic intracerebral hemorrhage (sICH) Study design • Observational studies (prospective or retrospective cohort studies, case-control studies) Exclusion criteria • Reviews, meta-analyses, conference abstracts, editorials, letters, and case reports • Animal studies • Non-English language publications • Studies without pre-treatment biomarker assessment • Studies without mRS-based outcome reporting 3. Information sources and search strategy Information sources A comprehensive systematic literature search was conducted in the following electronic databases: • PubMed / MEDLINE • Cochrane Library • Web of Science • Scopus No publication date restrictions were applied. The final search was completed on November 30, 2024. Search fields, filters, and results PubMed / MEDLINE • Search fields: All fields • Filters applied: o Article types: Adaptive Clinical Trial; Classical Article; Clinical Study; Clinical Trial; Comparative Study; Controlled Clinical Trial; Multicenter Study; Observational Study; Pragmatic Clinical Trial; Randomized Controlled Trial; Validation Study o Language: English o Species: Humans o Age: Adults (≥19 years) Cochrane Library • Search fields: All text • Filters applied: o Article type: Trials o Language: English Web of Science • Search fields: All fields • Filters applied: o Document type: Article o Language: English o Review articles and publisher-invited reviews excluded Scopus • Search fields: All fields • Filters applied: o Document type: Article o Language: English Search terms The following search strategy was applied with database-specific adaptations: (“acute ischemic stroke”) AND (mRS OR “modified Rankin scale”) AND (reperfusion OR recanalization OR thrombolysis OR thrombectomy) AND ( cytokine OR chemokine OR “inflammatory marker” OR “inflammatory biomarker” OR “adhesion molecule” OR NET OR NETosis OR “neutrophil extracellular trap” OR IFN OR interferon OR TNF OR TGF OR CCL OR CXCL OR ICAM OR VCAM OR selectin OR interleukin OR IL OR G-CSF OR GM-CSF OR M-CSF OR CD OR VEGF OR angiogenin OR “C-reactive protein” OR procalcitonin OR MPO OR “MPO-DNA” OR myeloperoxidase OR NE OR “NE-DNA” OR “neutrophil elastase” OR “citrullinated histone” ) 4. Study selection process Duplicate records were removed using EndNote reference management software. Two reviewers independently screened titles and abstracts. Full texts of potentially eligible studies were retrieved and assessed for eligibility. Disagreements were resolved by discussion and consensus. 5. Data extraction Two reviewers independently extracted data using a predefined data extraction form. Extracted data included: • First author and year of publication • Study design and sample size • Type of reperfusion therapy (IVT, MT, or both) • Inflammatory biomarkers assessed • Timing and method of biomarker measurement • Outcome definitions and follow-up duration • Adjusted odds ratios (ORs) with corresponding 95% confidence intervals • Confounders included in multivariable models If studies included both reperfusion-treated and non-treated patients, only data from the reperfusion-treated subgroup were extracted. 6. Risk of bias and quality assessment Study quality was assessed using a modified QUADAS-based tool consisting of 15 items rated as “yes”, “no”, or “unclear”. A total quality score (range: 0-15) was calculated for each study. All eligible studies were included regardless of quality score. 7. Data synthesis and statistical analysis Quantitative synthesis Meta-analyses were conducted for biomarkers reported in at least two studies with comparable outcome definitions. Adjusted odds ratios for poor functional outcome (mRS 3-6) were pooled using a random-effects model (DerSimonian-Laird method). Heterogeneity Between-study heterogeneity was assessed using Cochran’s Q test and quantified with the I² statistic. An I² value greater than 50% was considered indicative of substantial heterogeneity. Publication bias Publication bias was assessed visually using funnel plots when sufficient studies were available. No formal statistical tests were planned due to limited study numbers. Software All statistical analyses were performed using Stata version 17. 8. Subgroup and descriptive analyses Studies were categorized according to reperfusion modality (IVT, MT, or general reperfusion therapy). Biomarkers not eligible for meta-analysis were summarized descriptively. Secondary outcomes were recorded but not quantitatively pooled due to insufficient data. 9. Deviations from protocol The literature search was conducted prior to protocol registration. No deviations were made regarding eligibility criteria, primary outcome definition, or statistical analysis plan. Any future deviations would be transparently reported. 10. Registration statement This protocol is registered on the Open Science Framework (OSF) to provide a permanent, timestamped public record of the planned methodology.