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How to build the perfect search strategy: PubMed

22

February, 2019

PubMed is one of the biggest resources for literature monitoring, and it just keeps on growing. But the bigger the database, the tougher it is to pick up every relevant finding. That’s why you need a systematic, well-organized search strategy to help you catch all relevant information, no matter how much pages of results you have to click through.

PubMed is without a doubt one of the largest resources for literature screening in pharmacovigilance

Of course, there is no single, unified solution for conducting quality searches. Tactics differ from database to database, and from professional to professional.

However, good management and organization can really make your life easier when it comes to fishing out huge amounts of data during screenings. In this article, we’ll give you advice on building your own search strategy in PubMed, MEDLINE’s search engine of references and abstracts on life sciences and biomedical texts.

I. Starting a search

Get to know PubMed’s tools

First of all, you have to understand the scope and content of the database you search through. If you’re new to literature monitoring, you should make sure to check PubMed’s main features, such as filters and search options. Test them out and see if they can give you a well-needed boost in speed and accuracy.

Take the most out of My NCBI

Register on PubMed and you get more free tools to ease your monitoring. With them, you can save your searches so you don’t have to improvise with your browser’s history to backtrack your steps. My NCBI also allows you to expand your filtering options and make customized searches.

Catch all terms with MeSH

The Medical Subject Headings helps you find articles on the same topic that have different wording in their titles. It’s great for keeping track of all the terms from the MedDRA tree. MeSH matches the keywords you search with the closest MeSH terms.

The downside of this tool is that it works only with MEDLINE articles. However, assigning MeSH headings is still useful for literature screenings as it helps you make connections and get ideas for further terms you can explore.

It’s only logical

Boolean logic has been with us ever since the mostly self-taught mathematician George Boole introduced it in 1847. In today’s information age, it’s used in all modern programming languages, and in databases like PubMed to cover the variables of searches.

So the logical relationship between terms is based on the three Boolean operators: AND, OR, NOT. AND is the default and PubMed automatically connects your search terms with it.

When you type in more than one operator, the hierarchy of search terms is determined by the order in which you write them. When you enter more than one operator, the database will read them from left to right and conduct a search according to that order.

Remember to always type them in capital letters so PubMed can recognize them.

PubMed offers many tools that could increase the efficiency of searches. However, your own organization of the search is what helps get your workflow that extra boost you need.

Are you looking for a medicine or active substance?

Different rules apply when you search a substance and when you search a medicine. Some substances have one or several synonyms. Read through materials to find out what names you could use for the substance. Find synonyms.

This is especially important for PSURs. It is suggested that your periodical reports cover the whole drug class, not just the authorized medicinal product you are screening for your company or your client.

In Sympto® you can distinguish between medicinal products and substances, while linking findings to them at the same time. Depending on the report you are writing, you can look up either Substances or Medicinal products under the Products module. There you will find any additional information you can use during your literature search.

Set the right period

Determining the right start and end date of your searches is an easy, but crucial step in your monitoring. In PubMed, you can:

Determine a custom range

Unlike some other databases, PubMed allows you to pin down the exact dates for your searches. To appoint this custom range, find “Publication dates” and choose the start and end dates, and apply them to your search.

Use the PubMed Advanced Search Builder

You can use this tool to create a specialized search. Calculate the time period you need to cover. In case of PSURs, be sure to cover everything from DLP to DLP. The Builder offers you various search fields.

Turn off abstracts

You can use this tool to create a specialized search. Calculate the time period you need to cover. In case of PSURs, be sure to cover everything from DLP to DLP. The Builder offers you various search fields.

II.  Keywords

Sometimes, when you get a new client or medicinal product on your table, you have to cover an overwhelming period of time. PSURs spanning 4 or 5 years can yield about 15 000 hits, and common substances have a surplus of identical information.

This is when keywords become the key players in literature search. So, how to be sure which keywords to use? Here’s a quick guide

Get informed about the medicine or substance

Inform yourself about the medicine. If you know what is important regarding a certain medicine, you’ll easily derive keywords from that information. Sometimes there are small things that could determine the success of your literature search. For example, a simple google search would show you that amoxicillin has an alternative spelling of amoxycillin. It also has over hundreds of trade names and several synonyms across the world.

Make sure you’ve combined all keywords.

If you’ve read the SmPC attentively, you will know what keywords matter. There are always a handful of keywords you can always use in searches, such as those linked to sensitive groups. For example, ask yourself, is the substance metabolized through the liver? If so, then combine it with “hepatic”, “liver” and so on. You can check the Keywords filter in Sympto® for inspiration.

Have you missed anything?

After you’ve dried up all the keyword matches you can think of, you can backup your search by going through the results that you have been left out of your keyword combinations. They will be unmarked, blue, and easy to spot, so make sure you click on every article you wish to read to open it (upon opening the link turns purple). This way, it’s easy to filter through the remainder of your search and spot anything you’ve missed.

And always keep in mind that doing the keywords right is a prerequisite to cover every relevant article. When using Sympto®, you can look up information on earlier cases and literature findings through to make sure you have matched all possible keywords.

III. You have your results. Now what?

Check the source and title

The source of information is the first giveaway. The title also. Sometimes it will be outright obvious that these hits have no connection to the molecule’s safety profile.

But that doesn’t mean there is no possibility that it holds information you can use. There could be a single paragraph or sentence in the article that gives insight on its safety profile – insight that could be valuable. Be completely sure the article has no substantial information before you judge it is non-relevant. If you would like more tips on judging relevant literature during screening, take a look at our article on literature relevancy.

Be thorough

Go through every article, one by one. Open even those articles that don’t seem relevant at first. Aside from reading through the text, it’s always a smart idea to double-check yourself if you’ve caught each and every mention of the medicine or substance and its safety profile. Use a simple “Find on page” command at the end of your readthrough to be completely sure.

Context is king

Some side-effects are common, so it’s not a surprise if they come up with the medicine you monitor. But they can also imply an increase in their occurrence. Some side-effects have been recognized decades ago, but lack recent literature on them.

That’s why additional checkups are so relevant for understanding the context of a drug and for composing a compliant report. And that’s why your knowledge and medical judgment are so important in literature monitoring.

Mark cases to stand out

Bold them, paint them red or in a neon color you cannot miss. Keep in mind that the QC will have to check each and every case you find, so make sure that they are hard to miss.

Classify cases for a more efficient report composition

Is it a case? Is it a study? Is it a meta-analysis? If it is a study, then what kind of study? Comparative, non-clinical? Was there an ADR? Sometimes the deadline is too tight to get deeper into a literature finding and you list it simply as a “Study”.

Keep in mind that if you take the time to identify the type of study, you’ll be able to speed up the writing process by helping the writer identify the information he can extract from each study. It can also point out the relevancy of a specific finding. To make classification of studies easier, take a look at our checklists.

Double check everything you do

You might do everything meticulously the first time around. However, even if you weed through the results with complete care, you should still do another run through. No matter how much extra time it takes, always be sure nothing important is left out.

Comment

Keep in mind that the findings you draw out will be used in report writing. To make it easier for the medical writer to compose them, attach commentary to each finding. By doing so, you help increase the workflow as the person you hand the findings over won’t need to figure them out from scratch. In Sympto®, you can leave comments for yourself or your colleagues any time you enter a literature finding.

Is deciding what to include still fuzzy?

Alongside a well-organized approach, the key factor for bullet-proof literature screening is your medical judgment.

Building your medical judgment takes practice, and a lot of learning. But if you put an extra effort to educate yourself, you will get the hang of literature searches faster. The more you investigate, the clearer it will be. The best way to work on it is to:

Regularly read pages of regulatory authorities

Regulations are always changing, and PV is a discipline where new information are constantly emerging. Read the pages of global regulatory authorities, EMA, FDA, and your local regulatory authority to hone your knowledge and abilities.

Read through RSS that arrive at your company

If your company has a subscription to any RSS, be sure to read them as they come out. Discuss them with your colleagues, especially if there are any new advice you can use.

Read old PSURs

Reading PSURs is the best way to learn literature monitoring. Check out their Literature sections to read what findings were deemed relevant, and you could get more ideas for keyword combinations

Collaborate on PSUR writing

If you have a feeling of what is important for a specific PSUR segment, point it out in a comment or communicate it to others in your team in any way you can. Compare insights and information for greater understanding and easier workflows.

We’ve established that PubMed is one of the biggest and most commonly used databases in pharmacovigilance. However, there are many other databases out there. Most are local and highly specialized. How to build a search strategy for these databases? Find out in our next article.

Want to know more about this topic or about Sympto®?

We invite you to connect with us or download our study checklists to make your literature screening easier.

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