Which characteristic is essential for a journal to be indexed in MEDLINE?

A journal's ability to be indexed in MEDLINE is fundamentally tied to its adherence to specific quality criteria established by MEDLINE itself. These criteria encompass a range of factors that ensure the journal maintains rigorous standards in its editorial practices, peer review processes, and overall scientific integrity.

Quality criteria may include the journal's commitment to publishing original research, the credentials of its editorial board, adherence to ethical publication practices, and the degree of transparency in the peer review process. Ensuring that only high-quality, reliable research is indexed helps maintain the overall credibility and usefulness of the MEDLINE database for researchers, clinicians, and policymakers.

Other characteristics, such as the number of articles published annually, citation metrics, and subscription models, may impact a journal's reputation or visibility but are not essential to the indexing process itself. Thus, the most critical characteristic for a journal to be indexed in MEDLINE is its compliance with the established quality criteria.