You should evaluate how applicable your findings are to other groups. Relevance can be broadly defined as geographic relevance or field relevance.
For geographical relevance, you need to consider the worldwide impact of your findings. For example, studies investigating the link between polymorphisms (variations) in the cystathionine β-synthase gene and essential hypertension in Chinese patients may have limited applicability to other populations. Such a study would be more suitable for publication in a regional journal. But extending the study to include a larger sample would have more relevance to readers worldwide. You could study more than one population type, or conduct a meta-analysis. Then the study could be submitted to an international journal.
It may still be possible to publish findings with a regional focus in an international journal. You can persuade the journal editor that your results have implications that extend beyond geographic borders. Let’s say you are analyzing the outcomes of gastric cancer patients treated with chemotherapy in Japan. Such a regional study could also apply to other East Asians, or to Japanese patients living in other countries. As another example, an English questionnaire translated into Arabic might have implications for people in other countries who want to adapt this questionnaire into their own language.
For field relevance, you need to consider the impact of your findings across different fields. Let’s say you are evaluating heavy metal contamination of soils near schools. Such a study could be important not only for environmental scientists, but also for those in government policy and occupational health. Therefore, you would want to publish these findings in a broad-focused or interdisciplinary journal. That way, you can reach more potential readers.
If you have specialized or regional findings that are suitable for a broad-focused or international journal, explain this clearly in your cover letter. Otherwise, the editor may quickly reject your manuscript as unsuitable for their readers.