Mastering Search Strategies for Systematic Reviews

Why It Matters

A well-defined search strategy is crucial for ensuring the thoroughness and reliability of systematic reviews. By crafting a precise strategy, researchers can:

• Capture all relevant citations, reducing the risk of missing critical studies.
• Enable reproducibility, allowing others to validate and replicate the review process.
• Optimize resource use by balancing sensitivity (retrieving all relevant studies) and specificity (minimizing irrelevant results).

Key Aspects of Sensitivity and Specificity

A highly sensitive search is designed to include all relevant studies, even at the risk of retrieving some irrelevant ones. This minimizes the likelihood of omitting key studies. Specificity focuses on narrowing results to only the most pertinent studies, saving time during the screening process. Striking the right balance is essential for efficient and reliable systematic reviews.

Studies vs. Reports of Studies

A single study can produce multiple reports, each presenting unique details such as methodologies, outcomes, or follow-up results. Effective searches must identify all reports linked to a study to provide a comprehensive view of its findings. Researchers should focus on collating these reports to avoid duplication and ensure accuracy.

Medical Subject Headings (MeSH)

MeSH terms are standardized keywords used to categorize articles in databases like MEDLINE. These controlled vocabularies help overcome differences in terminology, ensuring that all relevant articles are retrieved regardless of the specific words used by authors. Leveraging MeSH terms enhances the consistency and depth of searches.

Boolean Operators and Filters

Boolean operators (AND, OR, NOT) enable researchers to combine search terms effectively, narrowing or broadening search results as needed. Filters further refine searches by restricting results to specific study types, languages, or publication dates, making the process more targeted and manageable.

Step 1: Identify Key Concepts

Begin by breaking down your research question into its core components, such as Population, Intervention, Comparator, and Outcomes (PICO). These elements provide a structured framework for identifying relevant search terms and concepts.

Step 2: Search for MeSH Terms

Access the MeSH database to identify controlled vocabulary terms that align with your research question. Starting with broad terms and gradually narrowing down to specific concepts ensures comprehensive coverage.

Step 3: Develop a Search Strategy for MEDLINE

Combine MeSH terms and free-text keywords using Boolean operators to create a robust search strategy for MEDLINE. Incorporate synonyms, alternate spellings, and acronyms to account for variations in terminology.

Step 4: Develop a Search Strategy for Non-MEDLINE Citations

For recent publications not yet indexed in MEDLINE, use flexible search techniques such as quotation marks for exact phrases, truncation for word variations, and wildcards for alternate spellings. This approach ensures the inclusion of cutting-edge studies.

Step 5: Combine the Search Strategies

Merge the results from MEDLINE and non-MEDLINE searches using the Boolean operator OR. This comprehensive master strategy captures all relevant studies from diverse sources.

Step 1: Choose Relevant Databases

Select databases that align with your research topic, considering their scope, comprehensiveness, and indexing practices. Common databases include MEDLINE, Embase, Cochrane Library, and subject-specific repositories.

Step 2: Execute and Export Searches

Run your master search strategy in each database, exporting results to reference management software like EndNote or Zotero. This streamlines the organization and screening process.

Step 3: Set Up Alerts

Automate updates by setting up search alerts in platforms like MyNCBI or similar tools in other databases. Alerts notify you of newly published studies that match your search criteria, ensuring your review remains current.

Step 4: Additional Search Techniques

Supplement your primary search with techniques such as backward citation searching (reviewing references of included studies) and forward citation searching (identifying studies that cite included articles). Engage with experts or study authors to identify unpublished or ongoing research.

Stage 1: Title and Abstract Screening

Review the titles and abstracts of retrieved studies to exclude those that are clearly irrelevant to your review. Use predefined inclusion and exclusion criteria to guide this process.

Stage 2: Full-Text Screening

Obtain the full texts of studies that pass the initial screening. Apply detailed eligibility criteria to finalize the list of studies to include in your systematic review.

Maintaining detailed records of your search process is critical for transparency and reproducibility. Document the following:

• Databases and platforms searched.
• Search strategies, including terms and operators used.
• Dates of searches and applied filters.
• Number of records retrieved at each stage.

Include these records in your review, allowing others to assess the comprehensiveness of your work and replicate your methodology if needed.

Language Restrictions

While restricting searches to specific languages may simplify the process, it risks excluding important studies and introducing bias. Consider the implications of language limitations and strive for inclusivity where possible. I mean, can't we just use a large language model to do it for us? Just be sure you are transparent about the tools you use in your protocol and the final report.

Grey Literature

Explore sources of grey literature, such as government reports, dissertations, and conference proceedings. These often include valuable unpublished studies that may not appear in traditional databases.

Publication Bias

Be mindful of publication bias, which occurs when studies with positive results are more likely to be published. Incorporating strategies like searching trial registries and contacting study authors can help address this issue.