Using a “gold standard” set to test your search

When developing a systematic search, it’s important to use an iterative approach, constantly tweaking and reevaluating your strategy to ensure relevant articles are captured (and hopefully, non-relevant articles are minimised).

Today, I’d like to share a trick that I frequently use when building my searches. First, develop a set of articles which are relevant to your topic. These are articles which should definitely be picked up by your search. The articles might come from researchers or your patrons, other team members on the systematic review, background scoping searches, google scholar, or any other number of places. The more variety in the set of articles, the better. These articles will comprise your “gold standard set” by which you will test your search strategy.

PART 1: Formatting your PMIDs

First, put each of these articles into your citation management system (ideally EndNote). Next, ensure that each article contains a PMID (PubMed ID) in the accession number field (or whichever one you choose). In EndNote, this can often be easily done by clicking “references”, then “find reference updates”. However, do check through all the citations for any that are missed; it may be necessary to manually find the PMID in PubMed.

After you have your gold set all tidied up in EndNote, export the set of references using a custom output filter containing only the accession number field. To set this up in EndNote v7 (only required the first time you do this!):

  1. go to Edit -> Output Styles -> New Style.
  2. in the sidebar, find “Bibliography” heading and click the “Templates” subheading.
  3. in the box that says “Generic”, click “Insert Field”, then “Accession Number”. Save and close your output filter with a descriptive name such as “PMID”.

To export the references using your new filter, first make sure that your newly created output filter is selected (the name should appear in the dropdown box on the top header; if not select the dropdown box, then “select another style”). Next, press ctrl + A to select all references, then right-hand click and select “copy formatted”.

Open a word document and press ctrl + v to paste your formatted references. Your document ought to contain a list of PMIDs – one per line. From here, I use the find and replace tool to automatically format the list of PMIDs for Ovid Medline:

  1. Click “find and replace”.
  2. In the “find what” box, enter ^p (this stands for the paragraph character)
  3. In the “replace with box”, enter “_OR_” (the underscores represent spaces)
  4. Press “Replace all”.

findandreplace

Okay! Still with me? Your word document should be formatted most of the way. Now, I finish by adding an open parenthesis at the beginning of the document and replacing the final ” OR sequence with ).ui. The .ui at the end refers to the Ovid Medline field code for accession number (where the PMID is stored). The text of your document should now look something like this:

(“19901971” OR “22214755” OR “22214756” OR “24169943” OR “24311990” OR “18794216” OR “25491195” OR “16931779” OR “9727760” OR “22529271” OR “18757621” OR “25536072” OR “24838102” OR “25025477” OR “23460252” OR “26888209” OR “24381228” OR “25154608” OR “21889426” OR “24165853” OR “25315132” OR “26819213” OR “26936902” OR “27492817” OR “27531721” OR “27522246” OR “27067893”).ui

This process might take a little while to set up the first time, but once everything is automated through your custom output file, it will only take a few seconds in the future. I’m a big fan of front-loading my work to make things easier down the line.

PART 2: Testing your gold standard set

Now, navigate to your draft search strategy in Ovid Medline and paste the full query from part 1 into a new line below the search.

Take the line of your final search results and the line containing your gold standard set and OR them together. If the last two lines in Ovid contain the same number, you’re in luck! All the citations in your gold standard set will be picked up in your draft search. If not, NOT out your original search results to see which ones have been missed; by looking at these citations, you can strategise ways to pick up articles with similar wording or indexing.

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OR together your “gold standard” set with your final search results. If the number stays the same, all your gold standard articles are contained in the search strategy.

I sometimes find that researchers are concerned about whether the relevant articles they have found will be captured by my search strategies, so I sometimes include this “gold standard search” in draft strategies that I send. I also annotate my process to make it more clear.

The beauty of this method is that as new relevant papers are discovered from additional sources, you can add them to the gold standard set, and continually check your strategy throughout the drafting process.

How to make screening less painful

You know that feeling when you are running searches for a patron, and want to pick out some of the most relevant papers for them, but it’s a Friday afternoon and your eyes are tired and zomg screening is the worst?

I’ve got a tip to make this process marginally less awful. This life-saving tip comes from a wonderful colleague at the College of Physicians and Surgeons of British Columbia.

First, run your search(es) and download your citations into EndNote (or another citation management program)* for screening. Generally, I only use this tip for general scoping (not for systematic review screening), so I usually end up downloading less than 200 citations for this process, and sometimes as few as 30.

Next, export your citations into a .rtf format with an export filter that includes both the citation information and the abstract. To do this in EndNote (v7), go to the dropdown menu at the top of the page and choose “select another style…”, then search for “annotated”. Click the one with the category “generic”, then click “choose”. You will notice that the preview pane for each citation now contains the citation’s information and its’ abstract.

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EndNote dropdown menu and preview pane

Next, export your references by clicking the blue arrow on the top bar. First, press ctrl + a to select all the references. Then save the filetype as .rtf and select “annotated” as your output style. Save the file wherever, then navigate to that folder and open it. It should automatically open in Microsoft Word (or the word processing program of your choice). The file should contain all of your references, with abstracts.

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exporting your references from EndNote

Now comes the fun bit! Press ctrl + H (or click “replace” in the main top bar). Under “find what”, type one of the main terms for your first concept. Then click anywhere in the “replace with” box, but instead of typing anything, click “More >>” to expand the options, then click the “format” dropdown box, then “highlight”. The word “highlight” ought to appear below the “replace with box”.

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Find and Replace in Microsoft Word

Still with me? Okay. Click “replace all”. Repeat this step with other terms that might be found in the titles and abstracts of the citations (but only for your first concept!). Once you have reached relative saturation, click the highlighter icon in the main top bar, and select a different highlighter colour. Next, repeat the same process as above with your second main concept, until you have reached relative saturation.

Ta da! At this point, you ought to have a pretty colour-coded document which helps you easily see the main concepts from your search. Screening this word document will be much less straining on the eyes and take less time because the main concepts have already been identified for you.

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Word document, ready for screening

This trick works better for some topics than others. My example above which uses the concepts of caring and attachment works pretty well. However, complex interventions or other areas with ever-changing terminology might not work as well.

Pro tip: in some cases, it is useful to send this colour coded document to your patron, and let them make decisions about what citations are relevant.

Another pro tip: instead of formatting with a highlighter, which only comes in garish colours (why, microsoft? why??), you can also format the text in any way you want. For example, you can put the relevant terms in bold or italics, or make the text itself different colours.

That’s it for today. Have you ever done this, or something similar? Do you have any protips for screening more quickly and efficiently? Send them to me on Twitter or through the Contact Me form!

* But seriously, if you’re not using EndNote, get on that.