Designing a search strategy in a bibliographic database is complex. Thus, working with a professional librarian to develop your search strategy is necessary.

Librarians have expertise for information retrieval within bibliographic databases and online resources. Specialized librarians must design and are responsible for the search strategies for systematic mixed studies reviews to find the proper search strategy and identify the best filters to find the quantitative, qualitative and mixed methods studies relevant for your review question(s). For non-systematic reviews, librarians should be consulted (at least to save time/energy and conduct a trustworthy search).  In general, there are 6 main steps to follow: (1) Identify the key concepts of your review question, (2) determine the search terms, (2) combine the search terms, (4) limit the search, (5) export results to a reference manager software, and (6) remove duplicates.

The content of this page was adapted from a presentation on “Searching the literature for Mixed Methods Research” offered by Mr. Martin Morris and Ms. Genevieve Gore, liaison librarians at McGill University.

 IDENTIFY THE KEY CONCEPTS OF YOUR REVIEW QUESTION

To search for relevant papers on your review question, you need first to identify the key concepts. For example, to the question, “What is the effectiveness of aspirin for preventing heart attack?”, the key concepts are: effectiveness, aspirin, prevention, heart attack.

FOR EACH CONCEPT, DETERMINE THE SEARCH TERMS

From the concepts identified, you will have to generate a list of terms to search databases. There are two main types of search terms: subject heading and keywords. The following table compares both types:

Tips for search by keyword terms:

When searching keyword terms, there are several operators and wild card characters that can be used to make sure you do not miss relevant records. Here are some operators used in OVID (if you use another interface, check the operators used):

Searching papers using a specific study designs:

Bibliographic databases can contain specific indexing to retrieve quantitative studies, which facilitates the retrieval of a particular study design such as randomized controlled trials for instance. However, they do not have (yet) specific indexes or filters for seeking mixed methods studies or qualitative research studies. 

Searching mixed methods studies:

We propose a generic strategy for retrieving mixed methods studies: 

• Text-word search: ‘(quantitative AND qualitative) OR mixed method* OR multi ADJ method’ 

Searching qualitative studies:

To locate qualitative studies, the following articles offer search filters for various databases. Of those, one permits to compare the sensibility and specificity of search strategies by database (Grant, 2004), and one suggests usual search strategies by qualitative researchers (search by list of designs) (McKibbon et al., 2006). 

Higher Sensitivity Search Strategies for Retrieving Qualitative Studies (McKibbon et al., 2006, p. 451)

 NOTE: exp = explode (in a thesaurus, gathering all components of a term). See database vendor for fuller explanations of searching techniques; mp = multiple posting (term appears in title, abstract, or subject heading); sh = indexing term used by indexers of the database content; tw = words or phrases in the title or abstract; : = truncation indication picking up multiple endings of words and phrases; px = psychology subheading; fs = floating subheading.

Searching empirical studies:

We have recently developed a search filter to identify empirical papers in databases (quantitative, qualitative and mixed methods studies) (see filter developed in Medline).  This filter was found to be performant with high sensitivity and specificity.

Reference: El Sherif, R., Pluye, P., Gore, G., Granikov, V., & Hong, Q. N. (2016). Performance of a mixed filter to identify relevant studies for mixed studies reviews. Journal of the Medical Library Association, 104(1), 47-51.

If you want to read more about filters for qualitative and mixed methods studies, here are some references:

• Grant MJ. (2004). How does your searching grow? A survey of search preferences and the use of optimal search strategies in the identification of qualitative research. Health Information & Libraries Journal, 21, 21-32.
• McKibbon KA, Wilczynski NL, Haynes RB. (2006). Developing optimal search strategies for retrieving qualitative studies in PsycINFO. Evaluation & the Health Professions, 29(4), 440-454.
• Walters LA, Wilczynski NL, Haynes RB. (2006). Developing optimal search strategies for retrieving clinically relevant qualitative studies in EMBASE. Qualitative Health Research, 16(1),162-168.
• Wilczynski NL, Marks S, Haynes RB. (2007). Search strategies for identifying qualitative studies in CINAHL. Qualitative Health Research, 17(5), 705-710.
• Wong SS, Wilczynski NL, Haynes RB. (2004). Developing optimal search strategies for detecting clinically relevant qualitative studies in MEDLINE. Studies in Health Technology and Informatics, 107(Pt 1), 311-316.

COMBINE YOUR SEARCH TERMS

Once you have identified the search terms related with your review questions, you have to combine them using Boolean operators. There are 2 main Boolean operators.

Supposed you have two main concepts, A and B.

• Using the expression A AND B will obtain records that contain all the search terms specified.  Each term must be present in every reference. This reduces the number of records.
• Using the expression A OR B will retrieve records that have at least one of the search terms. All terms do not have to be present in every reference. This increases the number of records.

In general, you will combine all the subject headings and keyword terms related to a same concept with the Boolean operator OR. The concepts are combined using AND. 

LIMIT THE SEARCH

There are different criteria available in a database to limit your search. These criteria can be useful to reduce the number of irrelevant records from your search strategy. For example, if you are only interested in papers published over the past 10 years, use the Year of publication criteria.  You can limit other criteria such as Languages, Publication type, and Age group.  

EXPORT RESULTS TO A REFERENCE MANAGER SOFTWARE

In most databases, it is possible to export the results of the search strategy to a reference manager software.  There are several available reference manager software such as Endnote, RefWorks, Papers, and Zotero.

REMOVE DUPLICATES

If you search in several databases, you need to deduplicate (i.e. eliminating duplicates). The deduplication should be done carefully following a clear method. For example, Bramer et al (2016) developed a deduplicate method in Endnnote. 

References

• Bramer WM, Giustini D, de Jonge GB, Holland L, & Bekhuis T. (2016). De-duplication of database search results for systematic reviews in EndNote. Journal of the Medical Library Association, 104(3), 240.
• El Sherif R, Pluye P, Gore G, Granikov V,  Hong QN. (2016). Performance of a mixed filter to identify relevant studies for mixed studies reviews. Journal of the Medical Library Association 104(1), 47-51.
• Grant MJ. (2004). How does your searching grow? A survey of search preferences and the use of optimal search strategies in the identification of qualitative research. Health Information & Libraries Journal, 21, 21-32.
• McKibbon KA, Wilczynski NL, Haynes RB. (2006). Developing optimal search strategies for retrieving qualitative studies in PsycINFO. Evaluation & the Health Professions, 29(4), 440-454.