Is it sometimes hard to find the specific information you are looking for in the medical literature? Maybe it is time to change your literature search strategy to speed up and improve your writing process. There are basically two things that are important for a good search: the search engine and the search terms you use.

Literature search engine

Many people start their literature search at Google, and there is nothing wrong with that if you are entirely new to a field and want to get a feel for the terms. For scientific or medical writing, however, you need sources that you can rely on to be accurate and trustworthy. So for searching scientific articles and reviews – these last ones are also a good starting point on a new subject- you may want to use PubMed  (over 30 million biomedical publications, including books). PMC is a database that also contains biomedical publications, except a lot fewer (over 6 million) than PubMed, as all publications in PMC are freely accessible. So if you want to avoid the frustration of finding a perfect publication and then not having access to it, you may want to use PMC instead of PubMed (or check out my blog on the many ways to obtain PDFs).

If you are looking for specific information on clinical trials that are planned, in progress, or completed you can find this information in clinical trials databases for the EU, the UK, and the US. A list of various other clinical trials databases you can find here.

Searching information in PubMed should not feel like looking for a needle in a haystack  (Image by Pete Linforth via Pixabay)

Literature search terms

The most basic search is with a combination of keywords, you can use this strategy in any search engine.  There are however many ways to narrow or broaden your literature search. The below options are geared towards PubMed and PMC but will also work with many other search engines:

• By using quotation marks you can look for a specific phrase. For instance, if you are looking for primary immunodeficiency you will get 32430 results in PubMed, while with “primary immunodeficiency” only 4670. With late onset combined immunodeficiency you get 111 results while “late onset combined immunodeficiency” returns only 15.

• By using square brackets you can indicate in which field your search term should be present. For instance, if you are looking for a publication in a specific year use “2018”[Date – Publication]. Or for a specific range of years use  (“1995″[Date – Publication] : “2020”[Date – Publication]), which can be useful if you want to review everything after a specific date. With hiv[Title] you can look specifically for HIV in the Title.  You can find these and many other options for advanced searching by clicking on Advanced right below the PubMed or PMC search box.

• By using AND, OR, and NOT you can further specify your search. For example, if you are looking for something on immunodeficiency but are tired of scrolling through the enormous amount of articles on HIV, you may want to exclude those by using a query such as (immunodeficiency) NOT hiv[Title] NOT “human immunodeficiency virus”[Title]. On the other hand, if you want to find all articles with HIV you may want to search for HIV OR “human immunodeficiency virus”.

Pre-set search options

• There are also several pre-set search options that can help you narrow down or broaden a specific topic or search strategy. You can find them here. They range from the very simple  ´all retracted publications´ to very extensive search strategies to find everything ever written on, for instance, AIDS. You can review the actual search strategies there as well.

• Another pre-set search option you may want to add to your search is the search strategy for systematic reviews that you can find here. With this search option you can retrieve all citations identified as systematic reviews, meta-analyses, reviews of clinical trials, evidence-based medicine, consensus development conferences, guidelines, and citations to articles from journals specializing in review studies. Instead of adding the complete list of search terms for this you can just add systematic [sb] to your search strategy.  For instance, by searching for “rheumatoid arthritis” you will get 135480 hits, while with “rheumatoid arthritis” systematic [sb] you only find 1406 publications.

Keeping up to date

• You can also keep up to date on a specific subject by using Create Alert. First you specify the search strategy, for instance, “chronic granulomatous disease” AND (mutation OR “genetic defect”) to –in this case- obtain all publications on mutations in CGD. Then you click on the Create Alert option below the search box. You need to create an account to have all new publications on this subject sent to your mailbox on a daily, weekly, or monthly basis. You can add other searches as well to create a weekly overview of all new publications in your field or by a specific author.

Additional tips

Tip: if you are writing a systematic review, meta-analysis, or similar report where systematic analysis of the literature is key, be sure to record the literature search strategy and the database searched. Many journals will want you to provide this information.

Tip: make sure you enter all publications that may be relevant into a reference management program right away. You can add notes and keywords, or group by subject. It will save a lot of time and hassle later on.