Library Tutorial for Public Health

Section 8. Advanced searching for higher degree students.

When you embark on a higher degree the dreaded literature review will loom large in your early preparations. It can seem rather daunting, but if you follow a few simple rules you'll save time, and avoid a lot of confusion and frustration. Essentially you are dealing with two simple components - language, and logic. This page is to help you with both.

Language - trawling PubMed for terms

Logic - constructing your search from the terms you've collected

Useful tips - to save you time

Other databases - moving on from PubMed to Scopus (my favourite) and other sources

Language

One of the problems we all have is that we expect other people to call things by the same name that we do. Even if they don't, in normal conversation this is not a problem, as we rapidly process the alternatives as equivalents. So if I talk about sickness, and you talk about illness it really doesn't matter, as we still understand one another. Databases (with very few exceptions) don't work like this. Instead they search only the exact words we use (including misspellings!). This means that for comprehensive searching you need to provide them with as many possible alternatives as you can. Some of them (like PubMed and PsycINFO) even have their own indexing language, or thesaurus which needs to be considered as well. PubMed has a thesaurus which is called MeSH - which is simply an acronym for Medical Subject Headings.

We'll presume you're starting with PubMed, and the topic I've chosen is - economic aspects of obesity.
Most postgraduate topics will have more components than this, but I'm using a simple example to demonstrate general principles.
At this stage we will just explore the language you'll need to use in your search, without worrying about how many, or how few articles your retrieve, or even how relevant most of them are.

Method

• Open a Word document and set up a logic grid - you'll need a column for each concept.

A	B
obesity	economics

• Perform a simple search, using your own words - economics AND obesity.

• Scroll through the results to see if there are any articles that look as if they're on your topic. What you'll need is one that includes

(PubMed - indexed for MEDLINE)

Very new material will be labelled either

(PubMed - as supplied by publisher)

or
(PubMed - in process)

and will not have indexing (MeSH) terms added to it.

• Once you have found a suitable article click on the title. This will display the article details, plus its abstract, and a link to enable you to view MeSH Terms.

• Clicking on the + sign will allow you to see the indexing (MeSH) terms which have been used to describe the content of the article.
  The article I will use here is

Paying for obesity: a changing landscape.
Simpson LA, Cooper J.
Pediatrics. 2009 Jun;123 Suppl 5:S301-7. Review.

and the indexing is

Terms with an asterisk after them are Major terms, and represent the most important subject aspects of the article. Those without an asterisk are Minor terms, and represent less important aspects of the article's content.

Many of the indexing terms in this example have /economics as a subheading.

When searching, using subheadings is very risky, as indexing at this level is rather variable. It is preferable to use economics[mh] - economics as a MeSH term. This will retrieve both Economics as a MeSH term, and economics as a subheading.

• Check it out in MeSH - there's a link to the MeSH Database in the drop down box from the Search box

• Look up Economics as a MeSH
  Economics has a large range of more specific terms in the hierarchy beneath it, and PubbMed's default is to search all of these. This is called "exploding" a term, and PubMed explodes all terms with more specific sub-categories listed.

• Look up Obesity as a MeSH
  Obesity also has a list of more specific subcategories

• Now udate your logic grid

A	B
obesity[mh]	economics[mh]

• Repeat this process with other articles which look relevant to see whether consistent indexing patterns emerge, and to extend your range of MeSH.

As new material in PubMed is not indexed, and as indexers, being human, are prone to error, or variation in the way they interpret the content of an article, words in titles and abstract need to be searched too.

• Add terms to the logic grid to allow for this - the list below is not intended to be comprehensive, but will give you an idea of how to build a search. Notice that when phrases are to be searched in titles and abstracts, inverted commas must be used to enclose the phrase, and ensure that words are not searched independently.

A	B
obesity[mh] obesity[tiab] obese[tiab]	economics[mh] models, economic[mh] economics[tiab] economic[tiab] "health care rationing"[tiab] cost[tiab] costs[tiab] costing[tiab] "health expenditure"[tiab] "burden of disease"[tiab]

Logic

When you have finished collecting terms you are ready to search. PubMed requires that Boolean operators are in upper case, so it's important when searching PubMed to use AND, OR, NOT to connect your search terms. PubMed's tutorial gives a clear explanation of how Boolean logic works.

You will need to OR the individual words in each column, and then AND the groups of words together - remembering to use brackets around the groups of terms from each column to preserve the logic of your search.

Useful Tips

• Click on Details to see how PubMed has interpreted your search

• Use the Citation display to see MeSH terms for articles

• Add [mh] when searching for Mesh terms
  eg. economics[mh]

• Use [mh:noexp] if you don't want to explode the search term
  eg. economics[mh:noexp] will search only for the term Economics, not those in the list below

• Use [majr] to restrict your search to major indexing terms only
  eg. economics[majr]

• Use [tiab] to search for words in titles and abstracts - this is essential for searching the most recent literature
  eg. economics[tiab]

• Expert Searching in PubMed
  This is a single page guide produced by the Countway Library at Harvard University. Don't be put off by the "expert" - it's a very useful and easy to follow guide with lots of examples to help you to take advantage of PubMed's incredible search power.

Other databases

There may well be other databases that are useful for your topic, and I've included a list of additional databases I think will be of use for public health.

The biggest of these is Scopus, and although it doesn't have the sophisticated subject search capability of PubMed it has some extremely useful features which will allow you to extend your search with very little effort.

• Try copying the title of a really good article from PubMed, and pasting it (enclosed in inverted commas) into the Scopus Search box.

• Set the in box to Article Title, and search

• Once the result is displayed click on Abstract +Refs

This will allow you to see

• the abstract for the article

• articles which have cited this article,

  

• the list of references from the bibliography at the end of the article, along with a link to other articles which have cited each reference

Each reference in the list also has links to full text, as well as its own abstract and references.