Should You Rerun the Exact Original Search or Revise It?

Does Consistency Mean Running Exactly the Same Search Again?

You have an existing literature review and its original search strategy. To update the review, should you simply rerun that search with a new date range, or should you change it?

There is an understandable argument for leaving it alone. Using the same strategy appears to preserve comparability between the original and updated searches. But databases change, terminology develops, indexing evolves, and the original strategy may contain weaknesses that are now apparent. A search can therefore be perfectly consistent with its predecessor and still be poorly suited to finding the current literature.

The decision is not really between consistency and improvement. It is about preserving methodological continuity where it remains defensible while making justified changes where necessary.

Rerun a Sound Search, but Revise It When There Is a Reason

The Original Search Is a Starting Point, Not an Untouchable Template

When rerunning the original strategy may be appropriate

If the review question and eligibility criteria are unchanged, the original search was well constructed, the terminology remains current, and the databases still operate in substantially compatible ways, rerunning the strategy for the new period may be the simplest defensible approach.

Cochrane's guidance for updating reviews specifically notes that in some cases the existing search can be rerun with date limits covering the period following the most recent search. It also recommends checking that the strategy remains appropriate rather than assuming that an old query can simply be reused indefinitely.

Why an exact rerun can sometimes miss relevant evidence

A search strategy is built for a particular question, vocabulary, database environment, and point in time. Any of those can change.

For example, a database may introduce or revise controlled vocabulary. A field may adopt a new term for an existing concept. A new intervention, technology, population label, or classification may become eligible under the review. The database interface or search syntax itself may also change. In these circumstances, entering the old query exactly as written may not reproduce its original retrieval behavior.

For an update, preserving the second is generally more important than mechanically preserving the first.

Revisit the review question before touching the search

The search strategy follows from what the review intends to include. If the question, scope, or eligibility criteria have changed, the search may also need to change.

Guidance on systematic review updating recommends revisiting the background, objectives, inclusion criteria, and methods before incorporating new studies. Search decisions should follow that methodological audit rather than precede it.

This is one reason updating an existing literature review should begin with an assessment of what remains valid rather than simply opening the old database queries and changing the dates.

New terminology can require more than a prospective change

Suppose a concept has acquired a new name since the original review. Adding that term to the updated search is sensible, but another question immediately appears: could older eligible records also have used that terminology and therefore have been missed previously?

If so, applying the new term only to recent years may be insufficient. Cochrane notes that when developments in a field produce new search terms, parts of the search may need to be rerun back to the earliest records. The appropriate response to changed terminology in an updated search therefore depends on when the terminology emerged and whether the original search could already retrieve the underlying concept.

Database changes can require technical adaptation

Even if your conceptual strategy has not changed, its implementation may need to. Controlled vocabulary, indexing practices, interfaces, and access mechanisms can change. Search syntax also differs across databases and platforms.

A strategy should therefore be checked in each source rather than copied mechanically from an old appendix. Where available, involving an information specialist or librarian can be particularly useful for complex systematic searches.

Use what the original search taught you

The first search produced evidence about its own performance. You now know which terms retrieved eligible studies, which sources contributed unique records, and perhaps which search concepts generated large quantities of irrelevant material.

Garner and colleagues specifically suggest that update searches may be refined using the yield of the previous search. That does not mean deleting apparently unproductive terms casually. A term that retrieved no included study previously could still retrieve an eligible future study. Rather, the previous yield can inform a reasoned assessment of whether the strategy can be made more efficient without compromising appropriate retrieval.

Do not preserve a weak strategy merely for comparability

If the original strategy was poorly designed, rerunning it faithfully perpetuates the same problem. Perhaps an important synonym was omitted, an inappropriate limit was applied, or relevant sources were not searched.

In that situation, the issue extends beyond how to search the new period. A weak original search strategy may have missed studies during the historical period as well. Repairing the search prospectively would leave that earlier gap unresolved.

Changing databases is a separate methodological decision

Search updates sometimes coincide with changes in available information sources. A database may no longer be accessible, another may have become relevant, or coverage may have changed.

The existence of new databases or information sources does not automatically mean that all of them should be added. Their relevance depends on the review question, disciplinary coverage, overlap with existing sources, and whether they could identify eligible evidence that the existing search is unlikely to capture.

Document the old strategy and the new strategy separately

If you revise a search, do not overwrite the historical record as though the new strategy had always been used. Readers need to know what was actually searched in each version of the review.

PRISMA-S emphasizes transparent, reproducible reporting of literature searches. For an update, that means retaining enough information about previous and current searches to show what was searched, when it was searched, and how the strategy changed.

When a Small Search Revision Creates a Historical Question

The methodological principle is simple: the goal is not to make the new query visually identical to the old one. It is to maintain defensible coverage of the review's eligible evidence.

Mistakes When Rerunning an Existing Search

Choose the Search That Best Preserves Valid Coverage

Whichever route you choose, preserve the audit trail. The original strategy tells readers how the earlier evidence was found; the updated strategy tells them how you searched now. Both can matter for understanding the review.

Before Rerunning an Original Search

Questions About Revising an Update Search

Consistency Does Not Require an Identical Search

How to Cite This Guide

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