Literature Search: A literature search will be conducted across the databases of PubMed, Embase and Cochrane. Keywords include "atrial fibrillation", "ischemic stroke", "N-terminal pro-brain natriuretic peptide", and "NT-proBNP". Additional studies are to be obtained from Google Scholar and from hand-searching within the references of previous studies. Inclusion and Exclusion Criteria: The study’s inclusion criteria includes: (1) patients diagnosed with AIS; (2) patients aged 18 years and above; (3) a defined cut-off value for high NT-proBNP levels; (4) availability of data on the number of AF and non-AF patients with NT-proBNP levels above and below the cut-off; and (5) studies with robust methodological design, requiring a minimum sample size of 20 patients. Criteria for exclusion include: (1) animal studies; (2) inaccessible studies where the complete report can not be retrieved; (3) studies published in languages other than English; and (4) studies sourced from the same database as another included study in the meta-analysis. Data Extraction: From the studies included in the meta-analysis, data is to be extracted and organized into a comprehensive spreadsheet. Information to be extracted includes study characteristics, stroke cohort, patient comorbidities, NT-proBNP cut-off level, and the number of patients below the NT-proBNP cut-off both with and without AF. Statistical analyses: STATA (Version 13.0, StataCorp, College Station, TX, USA) will be used for statistical analyses. The "midas" package in STATA will be used to perform meta-analyses, providing information on the pooled sensitivity, specificity, and the area under the receiver operating curve, which will be the primary measure of diagnostic accuracy.