Finding the Best Information using PubMed

prophylactic anticoagulation after hip fractures

The technique here is first to establish a good search string for the subject, then use the special filtering systems of PubMed to find reviews and randomized controlled trials on the subject.

First let's get a view of the size of the problem.

Go to the PubMed site and enter anticoagulation hip fracture (workshop instructions in green)

hipentry.gif (21004 bytes)

The result is a short list (20) and a strange one. It is hard to see what the first two citations have to do with the subject entered. However, we will leave that knotty problem in favour of solving our problem as rapidly as possible. Page down until you get to a paper that is in the subject. The one I chose was

hipcitn.gif (3493 bytes)

Click on the link to see the abstract.

A quick look at the abstract shows you that this type of paper is what you want. You would like to do a search which would produce ONLY this type of paper. You can do that by looking at the way this paper was indexed by NLM

Above the title of the paper is a dropdown menu which offers different ways to display. Choose Citation then click on Display

 

hipdropdn.gif (4701 bytes)

After the Abstract there is a list of "MeSH Terms"   These are the terms used in the special vocabulary of Medical Subject Headings which the NLM librarians use to index each paper.

hipmesh.gif (5906 bytes) You will note that Hip Fractures/complications and Thrombosis/prevention & control are both MeSH terms. One would expect that using these and defining them as MeSH terms would produce a list which is both comprehensive and sensitive.

All MeSH terms can have subheadings like /complications. In this situation we are interested in all Hip Fracture papers so we will use the term without the subheading.

Copy and paste the following search string into the PubMed box

hip fractures[mesh] AND thrombosis/prevention and control[mesh]

This results in a collection of 162 papers (in November 2001) going back to 1965. Almost all of them are on the subject so we have achieved the first objective, finding the right search string.

hiplist.gif (13574 bytes)

Now we want to refine the search and find those studies with the best methodology. PubMed has a special filter for that entitled "Clinical Queries"

Return to the PubMed page and locate the Clinical Queries link in the blue panel to the left of the screen.

Click on the link to Clinical Queries

hipcq.gif (2551 bytes)

The following screen shows the clinical queries dialogue page

Enter the search string in the box as shown. If you cut and pasted the search string before it will still be in your "clipboard" and you can paste it into the box. Note. Do this on the PubMed page, not on this one. The box does work but may scramble the presentation.

Clinical Queries using Research Methodology Filters

This specialized search is intended for clinicians and has built-in search "filters" based largely upon Haynes RB et al.. Four study categories--therapy, diagnosis, etiology, prognosis--are provided, and you may indicate whether you wish your search to be more sensitive (i.e., include most relevant articles but probably including some less relevant ones) or more specific (i.e. including mostly relevant articles but probably omit a few). See this table for details regarding filtering.

Indicate the category and emphasis below:
Category: therapy diagnosis etiology prognosis
Emphasis: sensitivity specificity

Enter subject search (do not repeat any of the words above):

NOTE: If you want to retrieve everything on a subject area, you should not use this page. The objective of filtering is to reduce the retrieval to articles that report research conducted with specific methodologies, and retrieval will be greatly reduced.

Click on the Search button and the "high specificity" search will be done. The result is a list of 22 double blind or placebo controlled trials of anticoagulation in hip fractures. Compare the list that you obtained to the link above. They should be more or less the same, allowing for the fact that new studies may be reported after Nov. 2001.

Now what has PubMed actually  done? As usual we can find out by clicking the Details button,

hipdet.gif (7113 bytes)

This looks unintelligible but close inspection shows that our search string (hip fractures and thrombosis prevention) is the start then there is a word salad linking "double" with "blind" blinded" etc. Right at the end (off the screen shot) there is also a reference to "placebo" The effect is to require some reference to double-blind or to placebo for the article to be included. This is the "specific" filter. The "sensitive" filter does something similar but looks for words that indicate a randomized trial type of format. This difference is important for surgeons since very few investigations of surgical treatment can be double blind or placebo controlled. DVT prophylaxis is one of the few surgical subjects which can be investigated in a double blinded RCT. Most of the time if you want to use these filters I suggest using the "sensitivity" filter for surgical procedures.

hipsens.gif (5041 bytes)

DIY filtering

These "bolt-on" filters may be helpful if you are in a hurry but as you get more familiar with the process you may wish to fashion your own filters adding Boolean terms to the search. This subject is treated in depth in the section on narrowing the search. One strategy which may be useful is to request review articles only. If you look at the end of the citations you will see that many of them are described as reviews. You can specify the publication type you wish to see.

Copy the string
hip fractures[mesh] AND thrombosis/prevention and control[mesh] AND review[publication type]
to the PubMed box and click on Go

PubMed will return 18 articles most of which are on the subject. If they are review articles they may be a more valuable entry into the literature that further struggl