Association between the levels of gamma-glutamyl transpeptidase and the risk of stroke: systematic review and meta-analysis

Figure 1. Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 flow diagram of the selection process of the primary studies included.

Figure 2. ( A ) Forest plot of the association between high Gamma-glutamyl transpeptidase (GGT) levels and hemorrhagic stroke in adults. All studies were initially included in the meta-analysis, which revealed high heterogeneity. After identifying outliers using Graphic Display of Heterogeneity (GOSH) analysis, the study by Ebrahim (2016) 25 was excluded. ( B ) Forest plot following the exclusion of outliers, demonstrating the association between high GGT levels and hemorrhagic stroke with acceptable heterogeneity.

Figure 3. ( A ) Forest plot of the association between high GGT levels and ischemic stroke in adults. All studies were initially included in the meta-analysis, which revealed high heterogeneity. After identifying outliers using GOSH analysis, the study by Wannamethee (2008) 27 was excluded. ( B ) Forest plot following the exclusion of outliers, demonstrating the association between high GGT levels and ischemic stroke with a slight reduction in heterogeneity.

Figure 4. Forest plot of the association between high GGT levels and subgroup analysis by sex: ( A ) in ischemic stroke; ( B ) in hemorrhagic stroke.

Figure 5. Funnel plot of the included studies in the meta-analysis on the association between high GGT levels and ( A ) ischemic stroke and ( B ) hemorrhagic stroke. Both plots suggest potential publication bias; however, this bias is not significant enough to impact the results.