What Should You Do if New Databases Have Become Available?

A New Database Exists. Should You Add It to the Update?

You are updating a literature review using the databases searched in the original version, but another database is now available. Perhaps it did not exist when the first review was conducted, your institution did not previously have access to it, or it has since expanded into literature relevant to your question.

Adding it may seem like an obvious improvement. More databases should mean a more comprehensive search, right? Not necessarily. Databases overlap, their coverage differs by field and publication type, and searching an additional source creates screening and documentation work. More importantly, adding a database to an update raises a historical question: if the database contains relevant older literature, should you search only the new period or search backward as well?

The decision should therefore be based on what the database contributes to the review, not simply on the fact that it is now available.

Add a New Database When It Meaningfully Improves Coverage

Evaluate What the New Database Adds to the Evidence Search

Start with coverage, not novelty

A database being new to you does not necessarily mean that it contains evidence missing from your review. It may substantially overlap the databases already searched. Conversely, a specialized database may index studies, conference proceedings, regional journals, dissertations, or disciplinary literature that your previous sources covered poorly.

Ask what types of eligible evidence the database indexes and whether those materials are relevant to the review question. Database selection is a methodological decision about information coverage, not a contest to produce the longest database list.

"New database" can mean several different things

The database itself may be newly created, but that is only one possibility. You may have gained institutional access to an established database. A previously irrelevant source may have expanded its coverage. Your review may have broadened into a discipline better represented elsewhere. Or you may simply have discovered a useful source that was available but omitted from the original search.

Look for complementary coverage rather than database count

Different databases index different combinations of journals, disciplines, geographic regions, study types, and other research outputs. The practical value of another database therefore depends on what it contributes beyond the sources already used.

For an interdisciplinary question, a database serving another relevant discipline may provide important complementary coverage. A review involving psychological, educational, medical, engineering, or social-science dimensions, for example, may require information sources that reflect those different literatures. The appropriate combination depends on the question.

At the same time, overlap is normal. Duplicate retrieval does not make a database useless, but extensive overlap with little unique relevant material may affect whether adding it is worthwhile.

Use the original review to learn about database yield

An update has one advantage that a new review does not: you already possess a set of included studies. Those studies can help you investigate how well different sources cover the evidence relevant to your question.

Methodological guidance on systematic review updating suggests examining the yield of the previous search in relation to the databases searched. In some circumstances, the search can even be made more efficient by concentrating on sources that adequately retrieve the relevant evidence. The reverse logic is also useful: if important included studies are absent from your existing sources but indexed in the newly available database, that may support adding it.

A new database creates a date-range decision

Suppose the original review searched Database A and Database B through December 2022. In 2026, you decide that Database C should also be searched. It would be convenient to search Database C only from January 2023 onward, but convenience does not establish adequate coverage.

If Database C contains eligible literature from before 2023 that was poorly represented in A and B, restricting it to the update period could preserve a historical gap. You therefore need to determine how far back the new source should be searched.

Do not confuse database age with record age

A recently launched database may contain records for literature published many years earlier. Similarly, gaining access to a database today says nothing about the publication dates of the material it indexes.

Before choosing a date limit, check the database's documented coverage and inspect relevant records. The question is not "When did we obtain this database?" but "Which eligible evidence could this database contribute that our previous searches did not adequately cover?"

Translate the strategy properly for the new source

Adding a database is not simply a matter of pasting the search from another platform. Databases differ in controlled vocabulary, field codes, phrase searching, truncation, proximity operators, limits, and other syntax.

The conceptual search can remain consistent while its technical implementation changes. The PRESS guideline identifies elements such as subject headings, text words, Boolean and proximity operators, spelling, syntax, and limits as important aspects of electronic search strategy quality. A strategy developed for one database should therefore be translated and checked for the new source rather than copied mechanically.

New database coverage may require new terminology

A newly added source may use different controlled vocabulary or index a discipline that describes the same concept differently. Database expansion and terminology updating can therefore interact.

If the source introduces another vocabulary into the search, check whether terminology has changed or differs across the literature. The aim is to represent the review concepts appropriately in that database, not to force the exact wording used elsewhere.

Adding a database can reveal a weakness in the original review

Sometimes the evaluation shows that the new source should clearly have been searched previously. Perhaps it indexes a central part of the literature that the original database set covered poorly.

In that situation, the methodological problem is no longer simply that a new database has become available. You may be dealing with a weak original search strategy whose historical coverage needs repair.

Report exactly which information sources were searched

PRISMA-S emphasizes transparent reporting of databases and other information sources, including the platform or provider where relevant. This matters because the same database can be accessed through different platforms, and search functionality may differ.

For an updated review, preserve the record of which sources were used previously and identify sources added, removed, or changed in the update. Readers should not have to reverse-engineer the search history from two versions of the manuscript.

Adding a Specialized Database During an Update

The important methodological choice is not the addition itself. It is deciding what evidence the new source can contribute and ensuring that the chosen date range does not leave an arbitrary gap.

Common Mistakes When New Databases Become Available

Ask What the Database Contributes Before Adding It

Do not begin with "How many databases should this review have?" Begin with the eligible evidence and ask where that evidence is likely to be found.

If a newly available source covers a relevant discipline, region, publication type, or body of literature inadequately represented by the existing search, adding it may strengthen the update. If it contributes little beyond sources already searched, its marginal value may be smaller.

The same reasoning should determine the search period. A source with distinctive historical coverage may need to be searched backward. A genuinely new source containing only recent material cannot contribute records from periods it does not cover.

Finally, incorporate this decision into the broader process of updating the literature review without discarding valid earlier work. Adding a database should solve an identifiable coverage problem, not create methodological decoration.

Before Adding a New Database

Questions About Adding Databases During an Update

A New Database Matters Only if It Changes Your Evidence Coverage

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