Adding Methodological Filters to MyNCBI

26 11 2009

Idea: Arnold Leenders
Text: “Laika”

Methodological Search Filters can help to narrow down a search by enriching for studies with a certain study design or methodology. PubMed has build-in methodological filters, the so called Clinical Queries for domains (like therapy and diagnosis) and for evidence based papers (like theSystematic Review subset” in Pubmed). These searches are often useful to quickly find evidence on a topic or to perform a CAT (Critical Appraised Topic). More exhaustive searches require broader  filters not incorporated in PubMed. (See Search Filters. 1. An Introduction.).

The Redesign of PubMed has made it more difficult to apply Clinical Queries after a search has been optimized. You can still go directly to the clinical queries (on the front page) and fill in some terms, but we rather advise to build the strategy first, check the terms and combine your search with filters afterwards.

Suppose you would like to find out whether spironolactone effectively reduces hirsutism in a female with PCOS (see 10+ 1 Pubmed Tips for Residents and their Instructors, Tip 9). You first check that the main concepts hirsutism and spironactone are o.k. (i.e. they map automatically with the correct MeSH). Applying the clinical queries at this stage would require you to scroll down the page each time you use them.

Instead you can use filters in My NCBI for that purpose. My NCBI is your (free) personal space for saving searches, results, PubMed preferences, for creating automatic email alerts and for creating Search Filters.
The My NCBI-option is at the upper right of the PubMed page. You first have to create a free account.

To activate or create filters, go to [1] My NCBI and click on [2] Search Filters.

Since our purpose is to make filters for PubMed, choose [3] PubMed from the list of NCBI-databases.

Under Frequently Requested Filters you find the most popular Limit options. You can choose any of the optional filters for future use. This works faster than searching for the appropriate limit each time. You can for instance use the filter for humans to exclude animals studies.

The Filters we are going to use are under “Browse Filters”, Subcategory Properties….

….. under Clinical Queries (Domains, i.e. therapy) and Subsets (Systematic Review Filters)

You can choose any filter you like. I choose the Systematic Review Filter (under Subsets) and the Therapy/Narrow Filter under  Clinical Queries.

In addition you can add custom filters. For instance you might want to add a sensitive Cochrane RCT filter, if you perform broad searches. Click Custom Filters, give the filter a name and copy/paste the search string you want to use as filter.

Control via “Run Filter” if the Filter works (the number of hits are shown) and SAVE the filter.

Next you have to activate the filters you want to use. Note there is a limit of five 15 filters (including custom filters) that can be selected and listed in My Filters. [edited: July 5th, hattip Tanya Feddern-Bekcan]

Under  My Filters you now see the Filters you have chosen or created.

From now on I can use these filters to limit my search. So lets go to my original search in “Advanced Search”. Unfiltered, search #3 (hirsutism  AND spironolactone) has 197 hits.

When you click on the number of hits you arrive at the results page.
At the right are the filters with the number of results of your search combined with these filters (between brackets).

When you click at the Systematic Reviews link you see the 11 results, most of them very relevant. Filters (except the Custom Filters) can be appended to the search (and thus saved) by clicking the yellow + button.

Each time you do a search (and you’re logged in into My NCBI)  the filtered results are automatically shown at the right.

Clinical Queries zijn vaak handig als je evidence zoekt of een CAT (Critical Appraised Topic) maakt. In de nieuwe versie van PubMed zijn de Clinical Queries echter moeilijker te vinden. Daarom is het handig om bepaalde ‘Clinical Queries’ op te nemen in ‘My NCBI’. Deze queries bevinden zich onder Browse Filters (mogelijkheid onder Search Filters)

Het is ook mogelijk speciale zoekfilters te creëeren, zoals b.v. het Cochrane highly sensitive filter voor RCT’s. Dit kan onder Custom Filters.

Controleer wel via ‘Run Filter” of het filter werkt en sla het daarna op.

Daarna moet je het filter nog activeren door het hokje aan te vinken. Dus je zou alle filters van de ‘Clinical study category’ kunnen opnemen en deze afhankelijk van het domein van de vraag kunnen activeren.

Zo heb je altijd alle filters bij de hand. De resultaten worden automatisch getoond (aan de rechterkant).

Reblog this post [with Zemanta]
Advertisements




Search Filters. 1. An Introduction

22 01 2009

I’ll be writing a lot about search filters in the near future. Before I do, I think it would be useful to give an introduction.

First I want to stress that this series will not deal with Google, Twitter etc. search filters. Although I might write about such filters on another occasion, this series is about filters for biomedical bibliographic databases, such as MEDLINE (PubMed) or EMBASE.

Below is a short Dutch presentation on search filters I gave at a symposium on search filters in 2005.[1] (some slides don’t show well in Slideshare)

What are search filters? [1-5]bmj-filters

Search filters are predefined and pretested search queries designed to retrieve selections of records in specified electronic information sources. Usually they are created by librarians, but they can be run by clinicians and researchers as well.

Why are search filters useful?

It is increasingly difficult, especially for the busy clinician, to find the information he/she wants in a database like PubMed. Filters can help to narrow down the search. In this way you can reduce the number needed to read (i.e. in a quick search) and/or increase the number of relevant papers (i.e. for a systematic review).

Different classes of filters:

  • Subject vs Methodological Filters
  • Sensitive vs Specific Filters
    • Sensitive filters are broad filters, designed to find as much relevant papers as possible, often at the cost of much ‘noise’.
    • Specific filters are designed to find a small set of very relevant papers, with the risk of omission of a considerable number of relevant papers.
  • Short vs Long Filters
    Filters may be simple -even consisting of one single term- or may be complex. They can comprise keywords, text words or both.
  • Database and search-interface dependency
    Filters are usually designed for a specific database and interface. Not every filter that has been developed can be directly translated into another dat
    abase/platform because of different
    keywords terms, hierarchy of keywords, structure and commands. For instance in EMBASE Case Control Study (which is not strictly a controlled study) is a Narrower term of Controlled Study, together with Controlled Clinical Trial. In MEDLINE Case-Control Studies‘ is considered an epidemiologic study, whereas Controlled Clinical Trials is a Publication Type. Note that the MESH is in the plural form: ‘Case-Control Studies
    The OVID platform allows separate searching of the abstract field (command: .ab.), whereas PubMed has no separate command for this ([tiab], title and abstract). Adjacency searching and non-explosion of subheadings (qualifiers of a MeSH term) is also possible in OVID, but not in PubMed.
    controlled-clinical-trial-embase-medline-90
  • Time dependency
    The performance of a filter may change over time because other terms may prevail or database keywords may have been added, removed or changed. In PubMed for instance the MeSH Randomized controlled trial has been changed in the MeSH Randomized controlled trial as a topic.
  • Subjective vs Objective Filters.[1,2]
    • The 1st generation of filters are subjectively derived, based on the expertise of the searcher.
    • 2nd generation is also subjectively derived, but then tested and validated against a gold standard, i.e. a known set of relevant records, to determine the effectiveness of the filter at retrieving relevant records.
    • 3rd generation involve objective approaches to filter design (e.g. frequency analysis or logistic regression). Search filter is tested on an independent set of known relevant records (gold standard).
      Whether filters are broadly applicable to different clinical areas will depend on the choice of the golden standard (subject, publication year, size) and the presence and composition of an extern valididity standard (a set of records different from the records used to develop the filter, against which the developed filter is tested)

Performance measures (for 2nd and 3rd generation filters), Figure adapted from [9]

Sensitivity: The number of relevant records retrieved by the search filter as a proportion of the total number of records in the gold standard.(A/A+C)
Specificity: The number of records that are not relevant and are not retrieved as a proportion of the total number of records.(D/D+B)
Precision: (
or positive predictive value), fraction of returned positives that are true positives. (A/(A+B)

2x2-search-filter

Is there any difference between search filters and limits?

Not really, both are search terms that can be used to narrow the search. In PubMed however limits usually consist of ONE single MeSH-term (MEDLINE Subject Headings, i.e. key words assigned by MEDLINE-indexers), thus these limits will miss recent papers that have not been indexed by MEDLINE. Therefore it is often safer to use a broader filter or no limit at all.

For instance consider the search tinnitus AND behavioral treatment (set #1 in the Fig. below). This yields 175 hits.
Most people, if they want to find the best individual studies limit for RCT, i.e. the subject search is combined (ANDed) with “randomized controlled trial[Publication Type]”. This yields 23 hits (#2).
However if they would have combined ther search with the narrow therapy-filter (#3) they would have found 3 extra hits, two of which being RCT’s, but still in process and not indexed:

1: Weise C et al Biofeedback-based behavioral treatment for chronic tinnitus: results of a randomized controlled trial.J Consult Clin Psychol. 2008 Dec;76(6):1046-57.
2: Kaldo V, et al Internet versus group cognitive-behavioral treatment of distress associated with tinnitus: a randomized controlled trial.
Behav Ther. 2008 Dec;39(4):348-59. Epub 2008 Apr 20.

The narrow therapy filter has found these very recent articles, because it not only searches for randomized controlled trial[Publication Type], but also for randomized AND controlled AND trial in title and abstract.
The broad therapy filter (#4) searches for clinical trials in general and finds many clinical trials that are not RCT’s.
The narrow (#5) and broad (#6) Cochrane RCT-filters are highly sensitive search strategies meant to identify randomized controlled filters for a Cochrane Review (see 10).

Thus for a quick search for relevant papers search #3 (narrow therapy filter) is most optimal.

search-met-diverse-filters

References

  1. Limpens J [ppt] Introductie Zoekfilters 2005 (Dutch)
  2. Booth A (Scharr) [ppt] Quality Search Filters at http://www.le.ac.uk/li/lgh/library/ABooth.ppt
  3. Jenkins M. Evaluation of methodological search filters–a review. Health Info Libr J. 2004 Sep;21(3):148-63.
  4. Glanville J, Bayliss S, Booth A et al So many filters, so little time: the development of a search filter appraisal checklist.J Med Libr Assoc. 2008 Oct;96(4):356-61.
  5. UBC Health LiBrary wiki: Systematic_review_searching and Filters (ie.hedges)
  6. Haynes RB, Wilczynski N, McKibbon, KA et al. Developing optimal search strategies for detecting clinically sound studies in Medline. J Am Med Inform Assoc. 1994 Nov-Dec;1(6):447-58.
  7. PubMed Clinical Queries
  8. Systematic review subset in PubMed
  9. McKibbon, KA, Wilczynski, NL, Haynes, RB Retrieving randomized controlled trials from medline: a comparison of 38 published search filters. Health Info Libr J. 2008.
  10. Post: New Cochrane Handbook: Altered Search Policies.