Synonyms are generally provided by a PUBMED feature called Automatic Term Mapping.

Example 1:

To give an example, say I want to search for articles on the evidence-based use of nutraceuticals (natural agents) for breast cancer prevention. This is the query I would type:

"breast cancer" evidence-based prevention nutraceuticals

Then once the search is performed by PUBMED, you will see off on the right-hand side of the page, a section marked "SEARCH DETAILS" and this shows precisely how PUBMED interpreted and expanded your query, using Automatic Term Mapping and the MESH system of filters it uses.

To see the location of the Search Details on the page, check out:

http://www.nlm.nih.gov/bsd/disted/pubmedtutorial/020_040.html

For the query above, the Search Details are:

"breast cancer"[All Fields] AND (evidence-based[All Fields] AND ("prevention and control"[Subheading] OR ("prevention"[All Fields] AND "control"[All Fields]) OR "prevention and control"[All Fields] OR "prevention"[All Fields]) AND ("dietary supplements"[MeSH Terms] OR ("dietary"[All Fields] AND "supplements"[All Fields]) OR "dietary supplements"[All Fields] OR "nutraceuticals"[All Fields]))

Notice all I entered was "nutraceuticals" but PUBMED's Automatic Term Mapping expanded this to "supplements", "dietary supplements", and "nutraceuticals". Similarly, I entered "prevention" but PUBMED's Automatic Term Mapping expanded this to include "control", an internal synonym for prevention.

Example 2:

I am looking for information about the Vitamin D assay (test), so I type:

Q: ("vitamin d" OR 25(OH)D OR "25-hydroxyvitamin d") (test OR assay)

From this PUBMEB returns this as the Search Details:

("vitamin d"[All Fields] OR 25[All Fields] AND ("hydroxide ion"[Supplementary Concept] OR "hydroxide ion"[All Fields] OR "oh"[All Fields]) AND D[All Fields] OR "25-hydroxyvitamin d"[All Fields]) AND (("research design"[MeSH Terms] OR ("research"[All Fields] AND "design"[All Fields]) OR "research design"[All Fields] OR "test"[All Fields]) OR ("analysis"[Subheading] OR "analysis"[All Fields] OR "assay"[All Fields] OR "biological assay"[MeSH Terms] OR ("biological"[All Fields] AND "assay"[All Fields]) OR "biological assay"[All Fields]))

And note that it expanded my assay or test terms to include "analysis" and "biological assay".

Example 3:

I wish to find only Level 1 evidence (systematic reviews, meta-analyses, and RCTs) but only dating from 2011 up to 2013, so the PUBMED search query I enter is:

"vitamin d"[TI] ("systematic review" OR meta-analysis OR "randomized controlled trial" OR Cochrane) 2011:2013[DP]

where "DP" in brackets after a year numbe,r or a year range (yyyy:xxxx), means Date of Publication of the articles to be returned, and [TI] after a term means that that term must be in the title of the article.

You can get a list of all these special MESH fields at:

http://www.ncbi.nlm.nih.gov/books/NBK3827/#pubmedhelp.Search_Field_Descrip

From this PUBMEB returns this as the Search Details:

("vitamin d"[MeSH Terms] OR "vitamin d"[All Fields] OR "ergocalciferols"[MeSH Terms] OR "ergocalciferols"[All Fields]) AND "[TI] ("[All Fields] AND ("review"[Publication Type] OR "review literature as topic"[MeSH Terms] OR "systematic review"[All Fields]) AND ("meta-analysis"[Publication Type] OR "meta-analysis as topic"[MeSH Terms] OR "meta-analysis"[All Fields]) AND ("randomized controlled trial"[Publication Type] OR "randomized controlled trials as topic"[MeSH Terms] OR "randomized controlled trial"[All Fields] OR "randomised controlled trial"[All Fields]) OR Cochrane[All Fields] AND 2011[PDAT] : 2013[PDAT]

Now it has expanded "Vitamin D" with an internal synonym, "ergocalciferols", and has also supplied the British English / Canadian / AU/NZ (and European to a large extent) "randomised" as a synonym for randomized.

Learning More

1. Although there is an online help system for PUBMED, I find this 63 page tutorial in the form of a PDF to be superior (courtesy of Virginia Tech University), covering every aspect of PUBMED searching:

http://www.lib.vt.edu/help/handouts/databases/pubmed-medline.pdf

2. In addition, just for Quick Reference, there is a two page PUBMED "cheat sheet", also as PDF:

http://nnlm.gov/training/resources/pmtri.pdf

3. There are also three dedicated Video tutorials: (1) Use MeSH to Build a Better PubMed Query, (2) PubMed Advanced Search Builder and (3) Need the Full Text Article?, all available together here:

http://www.youtube.com/playlist?list=PLBD13A2628C7A9965

4. Finally there is no substitute for expert feedback: so although I am a medical researcher in advanced oncology, I also am a trainer, and teach Power Search Techniques in Medicine (mainly but not just PUBMED), so I would be glad to help, and you can run by me, here in this topic, any query you are attempting, and I will try to provide some feedback, tips and hints. And of course if you post any such query, others here can also comment.

Constantine Kaniklidis

Director of Medical Research,

No Surrender Breast Cancer Foundation (NSBCF)

European Association for Cancer Research (EACR)

Dear Constantine Kaniklidis ,

Your answer was so useful. Thank you very much for your time and consideration

There are three major ways for identification of related search terms.

1. Controlled vocabulary such as MeSH and EMTREE

2. Studying core papers (i.e. review) and early search results

3. Experts consultation

The Cochrane Library can also provide some relevant keywords, I did not compare the possible differences with Medline (Pubmed) though.

Please check Cochrane´s Handbook http://handbook.cochrane.org/chapter_6/6_4_11_1_the_cochrane_highly_sensitive_search_strategies_for.htm

According to the Handbook to retrieve all relevant records you should use most popular expression and the one with descriptors [MeSH], /exp and [mh_your keyword]

Probably the most effective way is to start with your own keywords and then build up your search strategy using also avaliable MeSH (Medical Subject Headings) dictionary. Almost any reasonable medical search engines have them. They usually have also an online guide avaliable with explanation and examples of efficient use. Good approach is to check whether the web site you use have MeSH. Try advanced search feature at PubMed or Cochrane. Having personal account will give you a treat - ability to store your searches and to set alerts to get new papers title delivered straight to your email inbox as they are being published.

The keywords you use to search for literature could strongly affect the results of your research. I think the keywords must rotate about your research topic and your research objectives. But the phrases should not be too long.

Start by any keywords that you know , then after reading the frist reults you can build an effective search keywords

Please check my link, I shared many good sources:

https://www.researchgate.net/post/All_you_need_for_structured_systematic_literature_review_paper

MeSH

This video easily shows how to select the best keywords for your research/review article! https://youtu.be/ZKa7LLz6r2k