Early-Phase Fluid Diagnostic Biomarkers in Acute Ischemic Stroke: An Umbrella Review

Background and Purpose Acute ischemic stroke (AIS) is a time-critical emergency in which rapid diagnosis within established therapeutic windows (≤ 4.5 h for intravenous thrombolysis; ≤ 6 h for mechanical thrombectomy) is essential to optimize outcomes. Fluid biomarkers offer a promising adjunct to clinical and neuroimaging assessment but their temporal dynamics in the acute phases remain incompletely characterized. Methods We performed an umbrella review of systematic reviews and meta-analyses evaluating fluid biomarkers in AIS versus controls or stroke mimics. Quantitative synthesis of primary studies (random-effects meta-analysis of standardised mean differences [eG]) was stratified by clinically relevant time windows. Heterogeneity (I2), small-study effects (Egger's test) and excess significance bias were assessed. Results We included 27 publications (18 biochemistry, 1 metabolomic, 10 transcriptomic, 5 cell-free-DNA). Across all time-points the largest effect sizes were observed for neuron-specific enolase (NSE), ischemia-modified albumin (IMA), d-Dimer, S100B, GFAP, and IL-6. Looking at metabolites, studies revealed early accumulation of lactate, succinate, glutamate and lysophosphatidylcholines, alongside depletion of arginine, citrulline and citrate, indicating anaerobic glycolysis, excitotoxicity and nitric-oxide impairment. A catalogue of 220 micro-RNAs (132 upregulated; 108 downregulated) identified robust markers (miR-16-5p, let-7e-5p, miR-107, miR-451a and miR-126-3p) validated in ≥ 3 cohorts. 46 circulating-RNAs, and 55 long-non-coding-RNAs were consistently dysregulated. Five studies reported elevated nuclear (B-globin, TERT) and mitochondrial (MT-ND2; 2.5−3.5×) cfDNA within 6 h. Conclusions Fluid biomarkers exhibit a temporally evolving signature: early coagulopathy (D-dimer), glial activation (GFAP, S100B) and inflammation (IL-6), followed by neuronal necrosis (NSE) and oxidative stress (IMA) within 24 h. Multi-omic integration, including metabolomics, transcriptomics and cfDNA, highlights convergent pathways (PI3K/Akt, NF-κB, immunometabolism) and supports the development of rapid, point-of-care panels. Standardized sampling windows and harmonized assay protocols are essential for clinical translation and prospective validation in prehospital settings.