My name is Laurissa Gann and I’m a Medical Librarian at the RML.Today we’re going to talk about how to perform a literature search.All of you have searched the literature before, but I’m going to give you some tips on how to refine your search strategies, navigate the available databases, and become a more efficient searcher.
A well-structured literature search is the most effective and efficient way to locate sound evidence on the subject you are researching. In the age of the internet, it’s easy to think that information is easy to find because it’s online, at your fingertips. Literature can be found anywhere, in books, journals, databases, government documents and the internet. The reality is that information is more abundant than ever. How do you find the specific information that you really want or need?
We’ll talk about how to develop your question. Having a well defined question will save you time when searching. What kind of question are we asking. What’s our topic? What is the search for? That will determine where we search. Once we’ve selected our database or tool, we’re going to dissect it. Most databases have a similar structure so we just need to know what to look for.
Most people approach a database like you would Google. You throw some search terms in and hope for the best. How many of you have typed something into PubMed and seemingly gotten back random results?It is important that the clinical question be focused and well thought out so that you arrive at the appropriate answer. Having a clear idea of what you are researching will keep you on track with your searching, saving you valuable time. A focused question will give you a better start with your search because it will help you determine appropriate keywords and limitations for your topic.
When forming your question, make sure you are specific about your research topic. Things to consider are:Patient or ProblemIt is important to define the patient population of interest.Specifically, one must consider patient characteristics that may affect outcome such as:treatmentsexAgeethnicity2) Intervention or Exposure (or prognostic factor or diagnostic test),What main intervention are you considering (medical, surgical, preventative)?therapy (treatment)- an intervention such as a new implant or new surgical technique prognosis (the ability to predict an outcome) – factors that may influence outcome such as smoking status or age; or a prediction rulediagnosis (the value of a diagnostic test) – diagnostic procedure of interest such as a new technology3) Comparison group(s)This is an optional section. What are the alternative benchmark or goldmark standards being considered, if any?Compare with placebo? Compare with no intervention? 4) Outcome(s)What is the estimated likelihood of a clinical outcome attributable to a specific disease, condition or injury?What do you want to do for these people? Maybe you want to see which is the most cost effective intervention, or maybe you want to see which is the most accurate diagnostic test. Here you must decide on what outcomes are important to your question. Here it is good to be specific and to aim for the most important outcomes. 5) Type of Study – What is the best study design to search for to find evidence to answer your clinical question. Breaking my topic down in this way has made me think about my topic in more detail. I have ideas for an initial search as well as ways to expand the search if I want to.
Meta-analysis: A statistical technique that summarizes the results of several studies in a single weighted estimate, in which more weight is given to results of studies with more events and sometimes to studies of higher quality. Systematic Review: a review in which specified and appropriate methods have been used to identify, appraise, and summarise studies addressing a defined question. It can, but need not, involve meta-analysis). In Clinical Evidence, the term systematic review refers to a systematic review of RCTs unless specified otherwise.Randomized Controlled Trial: a trial in which participants are randomly assigned to two or more groups: at least one (the experimental group) receiving an intervention that is being tested and another (the comparison or control group) receiving an alternative treatment or placebo. This design allows assessment of the relative effects of interventions. Controlled Clinical Trial: a trial in which participants are assigned to two or more different treatment groups. In Clinical Evidence, we use the term to refer to controlled trials in which treatment is assigned by a method other than random allocation. When the method of allocation is by random selection, the study is referred to as a randomized controlled trial (RCT). Non-randomized controlled trials are more likely to suffer from bias than RCTs.Cohort Study: a non-experimental study design that follows a group of people (a cohort), and then looks at how events differ among people within the group. A study that examines a cohort, which differs in respect to exposure to some suspected risk factor (e.g. smoking), is useful for trying to ascertain whether exposure is likely to cause specified events (e.g. lung cancer). Prospective cohort studies (which track participants forward in time) are more reliable than retrospective cohort studies.Case control study: a study design that examines a group of people who have experienced an event (usually an adverse event) and a group of people who have not experienced the same event, and looks at how exposure to suspect (usually noxious) agents differed between the two groups. This type of study design is most useful for trying to ascertain the cause of rare events, such as rare cancers.Case Series: analysis of series of people with the disease (there is no comparison group in case series).
A Literature Search Starts with a TopicThis was a hot topic earlier this year. BRCA Mutations and breast cancer. Many women who inherit a harmful BRCA1 or BRCA2 mutation will never develop breast or ovarian cancer. What we’re interested in is whether women who test positive for the BRCA1/2 mutation opt for prophylactic mastectomies. Even further, I’d like to know a percentage. In order to create a searchable question, we have to turn our topic into a question. A single topic can easily be turned into many different questions. Ask yourself, what do you want the literature to tell you?We could look at the cost effectiveness of the test, we could look at the rate of women who are diagnosed with breast cancer who test positive for the BRCA1/2. We could look at the effects of this media story on women’s decision making. We can’t just throw in a question into the search box and get a comprehensive set of results. In order to do a good, quality literature search we need to be a little more sophisticated. In order to create a searchable question, we have to turn our topic into a question.
We can’t just throw in a question into the search box and get a comprehensive set of results. In order to do a good, quality literature search we need to be a little more sophisticated. In order to create a searchable question, we have to break our question into parts. Here we’re looking at women who are potential BRCA mutation carriers, and how predictive testing affects their decision to address the risk with a prophylactic mastectomy. Ovid MedlineBreast NeoplasmsBRCA1/BRCA2MastectomyRisk FactorsRisk AssessmentRetrospective Studies
Look for synonyms. Synonyms are the equivalent of the word. Make a list of terms for each part of your question. When you start searching you may come across new terms.
PubMed covers a large portion of the biomedical literature, but there’s a lot of biomedical information that PubMed does not contain. In order to avoid having a biases view of the literature, you need to include information from as a wide a selection of journals as you can. It’s a common misconception that every medical database contains the same information and while they do overlap some, they each have quite a bit of unique content in them. A literature search requires time and flexibility. You have to search more than one database to say that you’ve comprehensively found all applicable literature.
Quick & Dirty: When you need the answer fast!Usually can be answered with one database or tool. We often call these decision supporttools. Access these on your smartphone or tablet. These tools search monographs of a topic that will give you an overview of the subject. DynaMed:Evidence-based monographs,Includes Patient Information,Lexi-Comp and Natural StandardLexi-Comp:Collection of clinical databases,Drug, disease and toxicology monographs,MD Anderson FormularyUpToDate:Evidence-based monographs,Includes an image search,Patient Information hand-outs,Updated frequently,Incorporates Lexi-Comp for drug informationLiterature Search:When you are publishing or presenting professionally. This type of search requires a more thorough investigation and a search across multiple databases. Each database searches differentlyCochrane is where you will find systematic reviewsPubMed and SCOPUS will give you mid-level informationEmbase is a biomedical and pharmacological database which tends to be more comprehensive with inclusion of more EU journals as well as abstracts of scientific meetings. GoogleScholar – It covers a wide variety of subjects besides biomedicine. It also contains some information which is not academic peer-reviewed. Like PubMed, it does not include everything. PubMed & Google Scholar are good sources of information, but they shouldn’t be your only sources. If you’re not having success searching in one database, you can see that there are many other options.
Which databases you search is dependent again on your question. Background Search – This is when you need a quick answerLiterature review – To do your due diligence you will need to search 3 or 4 databasesSystematic Reviews – Require you to search at least five or six databases. This includes the Cochrane Library and Medline.
Most databases have a similar structure so we just need to know what to look for. We’re going to focus on PubMed but I want to show you several databases.
Phrase vs. Word searching: Does the database consider multiple words as a single phrase or a combinations of words connected by OR (any of the words), or AND (all of the words). Use OR searches to broaden your search. Use AND searches to narrow your search. Check to see what the default search is and also if other options are available. Truncation in PubMed is *Truncation in Medline is disease$ or h?ematologyALT + Tab“prophylactic mastectomy” “Prophylactic Mastectomy” OR Mastectomy“prophylactic Mastectomy” AND brca*“prophylactic mastectomy” AND brca* AND decision*Do MeSH search – 2 Parts, then combine with advanced(((("Genes, BRCA1"[Mesh]) OR "Genes, BRCA2"[Mesh]) AND "Mastectomy"[Mesh])) ((("Decision Making"[Mesh]) OR "Choice Behavior"[Mesh]) OR "Risk Reduction Behavior"[Mesh])18 unique results from keyword search
Check for limits. Most databases allow you to narrow your search by selecting specific dates, language, and publication types. Some databases allow you to restrict your search to particular population groups and ages. Some databases allow you to focus your search by adding special modifiers. This depends on the databases. In PubMed, you can limit your search to subset or try using the advanced search to limit to title and abstract search. (Search Advanced: brca* AND mastectomy AND percent*)One quick way to reduce your results and focus your search is to add one or more additional concepts to your search. Check to see if you can type mor terms into your search box or if you need to modify in another way. The search history feature will often allow you to combine your searches.
The more concepts you combine in a search, the fewer results you are likely to retrieve. If you get little or no results from your search, try eliminating some of you concepts, limits, modifiers. Many databases offer a “Related Articles” feature that enables you to expand your search. Clicking on a Related Articles link will allow you to retrieve more articles similar to the one with which you started. Another way to expand your results is to do a “Cited Reference Search” on any relevant article you might have. This feature is available in databases offered through Web of Science or Scopus. When you preform this type of search, you will retrieve articles that have cited the original article. You can use a cited reference search to find more up-to-date material on your topic, since retrieved material from this type of search will be more current than the origianl article.
Most databases offer the option of printing your results. Others also allow for e-mailing and/or downloading your results.
Literature Searching 101
PATHOLOGY Grand Rounds
A literature search is a well thought out
and organized search for all of the
literature published on a topic.
In PubMed, there are over 22
million citations for biomedical
literature to date
Approximately 712,000 citations
are added to PubMed every year
1, 950 articles per day.
81 articles per hour.
Today we will…
we can help at every step of the way
Find the best
Pose a searchable question
identify, consider, and focus
Creating the searchable question
What are the
characteristics of the
What is the condition
or disease you are
prognostic factor, or
exposure are you
What is the alternative
to the intervention
(e.g. placebo, different
What can you hope
measure, improve or
Choosing a Study Design
Type of Question Type of Study
An evaluation of a therapeutic or
Randomized Controlled Trial
Meta-Analysis of RCT
An evaluation of a test, screening or
other assessment such as history or
Meta-Analysis of Controlled
An evaluation of clinical outcomes
An evaluation of a therapeutic,
preventive, screening or diagnostic
intervention, or anon-therapeutic
exposure or behavior.
I want to know what the outcome of BRCA1/2
testing is for patients. Do most women who test
positive choose to have a preventative
decision for a
PM Type of Study
In BRCA mutation carriers,
what is the effect of predictive
testing on the decision for a
Choosing Search Terms
• Look for synonyms (flush, irrigate)
• Differences in spelling (Hematology, Haematology)
• Suffixes (Rheumatic, Rheumatology)
• Generic and trade names of drugs
Type of Study
In BRCA mutation carriers,
what is the effect of predictive
testing on the decision for a
Choosing Your Search Terms
Find the best places to
research, evaluate, and compile
The type of search determines where
you will search.
Decision Support Tools Search EnginesDatabases
How many databases should I search?
1 or 2
5 or 6
3 or 4
Dissect a database
expose, understand, and search
• Phrase versus Word
• Advanced Searching
What are the
of the database?
• Check for limit options?
• Are there any special
• Can you combine searches
or add more concepts to
your original search?
What do I do if I
get too many
• Eliminate concepts
• Look for related articles
• Cited reference search
What do I do if I
get too few
• Create an account to save
your search strategy or
• Find an export or output
button to download, save or
How do I print,
e-mail, save or
• Look for the MD Anderson
Full Text button.
How do I get the
Ask a librarian a question
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