Trial sequential analysis involving same-year studies requires careful temporal ordering.

Trial sequential analysis (TSA) is an increasingly used tool in systematic reviews to monitor synthesized evidence. However, the current practice of TSAs often overlooks the order of same-year studies, which are typically ordered alphabetically based on the last names of the studies' authors by default in the widely used TSA software application. This practice is inappropriate and contrary to the TSA's definition. This issue is particularly concerning in systematic reviews on time-sensitive topics, such as COVID-19, where reviews include many studies within a short period. In this article, we use a case study to illustrate the impact of the order of same-year studies on TSA conclusions. It shows dramatically different patterns of evidence accumulation when same-year studies are ordered alphabetically vs in their actual temporal order. This article offers suggestions for authors to pay attention to study ordering in future TSAs.