Indexation of a journal is considered a reflection of its quality. Indexed journals are considered to be of higher scientific quality as compared to non-indexed journals. Indexation of medical journals has become a debatable issue. For a long-time Index Medicus has been the most comprehensive index of medical scientific journal articles. It is being publication since 1879. Over the years, many other popular indexation services have developed. These include MedLine, PubMed, EMBASE, SCOPUS, EBSCO Publishing's Electronic Databases, SCIRUS among others. There are various regional and national versions of Index Medicus such as African Index Medicus.
A related and equally controversial issue is that of impact factor (IF). IF is used as a proxy for the relative importance of a journal within its field. IF is awarded to the journals indexed in Thomson Reuters Journal Citation Reports. IF has been criticised for manipulation and incorrect application. There are multiple factors that could bias the calculation of the IF. These include coverage and language preference of the database, procedures used to collect citations, algorithm used to calculate the IF, citation distribution of journals, online availability of publications, negative citations, preference of journal publishers for articles of a certain type, publication lag, citing behaviour across subjects, and possibility of exertion of influence from journal editors. Interestingly, IF is not available for all indexed journals. In fact, not all journals indexed even in Index Medicus/MedLine/PubMed are indexed in the Thomson Reuters Journal Citation Reports. Similarly, not all journals indexed in Thomson Reuters Journal Citation Reports and consequently have an IF are listed in Index Medicus/PubMed/MedLine.
This brings us to the question which indexation is best and most valid? How to compare the quality of articles published in journals indexed with different indexation services? These questions are of particular relevance for two main reasons. First, importance of publications is being increasingly recognised by the academic institutions. MCI guidelines also recommend indexed publications for teaching faculty in medical colleges. Consequently many more authors would be publishing than ever before. Selection of high quality journal becomes a difficult decision for the authors as there is no clarity on the issue. Should one aim at only the journals indexed in Index Medicus/MedLine/PubMed? Is it appropriate to make submissions to journals having a high impact factor although they are not indexed with Index Medicus/MedLine/PubMed?
Second, recently many more indexation services have come up. These include Caspur, DOAJ, Expanded Academic ASAP, Genamics Journal Seek, Hinari, Index Copernicus, Open J Gate, Primo Central, Pro Quest, SCOLOAR, SIIC databases, Summon by Serial Solutions, Ulrich's International Periodical Directory. Are these indexations services equally relevant? Would a journal indexed with any of these databases be considered “indexed”?
These are some questions that warrant discussion. Associations of editors of medical journals such as International Committee of Medical Journal Editors could play a pivotal role in such discussion.