Rhetorical structure and authorial positioning in medical research article introductions: a corpus-based comparison of articles published in selected Vietnamese and international journals

This study compares rhetorical structure and selected resources of authorial positioning in 154 English-language medical research article introductions published during 2021–2025. The Vietnamese and international journal samples contain 89 and 65 articles, with 37,650 and 34,452 Introduction words. An adapted CARS inventory identifies rhetorical functions; hedges and self-mentions are examined alongside a separate grammatical measure of overt be-passives. Explicit knowledge gaps occur in 66.3% and 93.8% of introductions, respectively (Holm-adjusted p<.001). Continuation of earlier work is also more frequent in the final IJI coding, although this category requires context-sensitive interpretation. None of the three linguistic comparisons reaches the adjusted .05 threshold. The findings provide examples for teaching research justification and author positioning. Sample composition and context-sensitive coding limit broader inference.