Tracking down the best available evidence to answer your question 

Once you have defined your question you will need to look for research evidence to help you find an answer. Where you look will depend on the type of question and what is available to you.

Here you will learn:

  • How to define the search terms
  • What type of evidence sources are appropriate to answer your question
  • Where to look for the evidence

Getting started

You can begin initial searches for research evidence using the keyword terms entered in your PICO (or similar) template used to define your question. Use each of these to run an initial search in one of the databases of peer-reviewed literature or within a specific journal. To find articles containing all of the key words combine the search terms using the Boolean connector ‘AND’. For example: paediatric AND life-limiting illness AND pain.

Once you have identified a relevant article(s) addressing your question, you can expand the list of search terms by using the article’s keywords. These are often included as part of the article's abstract.

When you have your complete list of search terms move on to searching your evidence source such as a pre-appraised collection or literature database to find more articles relevant to your question.

Advanced searching

As well as keywords, the often used PubMed database also uses Medical Subject Headings (MeSH terms). These terms or ‘tags’ are added to articles entered in the database so that similar articles can be retrieved even if the authors choose different keywords. It is a more efficient way to search for related articles. However, it takes time for these terms to be added and so keywords are also needed to capture more recent articles.

Note: If other groups working in your area of interest use similar but not identical terms your search may not capture all relevant research. An information specialist librarian can help you with this. If you do not have access to this service then consider using a validated search filter.

If you have access to the pdf of your article(s) you can also use one of the freely available Keyword Finder  tools for extracting keywords to help with this step.

    Example Keyword finders

PubReMiner - find suitable terms, relevant journals, and authors active in this field.

TerMine - Scan texts for high-frequency words and can be used with outputs such as EndNote generated abstracts to identify common terms across a set of articles.

Yale MeSH Analyser - Helps you to design a search strategy that includes all relevant keywords.

The 6S pyramid or hierarchy of evidence assists clinicians in deciding where to start with the most appropriate evidence. [1]

Synthesised evidence that considers evidence quality sits higher in the pyramid. So, you should start at the top and work your way down until you have identified relevant and useful evidence.

At the very top clinical guidelines and individual patient data are combined to guide personalised care. This is an emerging data application and you will find that most organisations do not yet have this level of support.

Guidelines (Summaries) are next and where available represent one of the best places to start your search for evidence in support of clinical decision-making. The evidence has been graded by experts based on strength, generalisability, and relevance of evidence, as well as applicability of any recommended changes to practice.

6S Evidence Pyramid

Beneath this you will find different forms of evidence summary (synopses of syntheses or single studies) and syntheses (systematic reviews and meta-analysis) of published research. These use rigorous approaches to identify bias and assess the quality of studies included in the review. Unlike guidelines they do not make recommendations. They may discuss the contexts of care and how the evidence might influence practice. Curated collections, journals, and databases can be used to identify these sources as well as individual studies.

At the bottom of the 6S Evidence Pyramid are individual studies. This is simply because it is not possible to know if outcomes from a single study are relevant to other groups, that is whether they can be generalised. However, it the population and context studied closely resembles your situation it may be useful.

Across each of the 6S levels a range of research study types might be drawn on including quantitative and qualitative research as appropriate. When selecting evidence from syntheses, synopses, and primary studies it is important to consider the Evidence hierarchy. But remember that although this guides us to select evidence based on methodology providing the greatest outcome certainty, the study designs required to achieve this are not always appropriate for some questions in palliative care. You can read more on Evidence Hierarchy in CareSearch.

Learn more

Complete the CareSearch learning module Finding Clinical Guidance. This module will explain how the Palliative Care guidelines, clinical Evidence pages, the Systematic Review collection and PubMed searches will assist you to provide better clinical care.


Guidelines help you by making generalisable recommendations based on systematic analysis of the evidence. Importantly, the quality and strength of evidence is taken into consideration. Where evidence is lacking or uncertain then expert consensus might be used to provide guidance. See CareSearch for palliative care guidelines.

In palliative care many people present with multimorbidity and comorbidities. However, guidelines often address only a single condition and following guidelines for each condition would be both complex and stressful for the person and health professional. It may be necessary for you to search beyond local or single disease guidelines to find evidence relevant to caring for someone with the comorbidities of your patient. Guidelines for comorbidities are beginning to emerge. The Australian RACGP aged care clinical guide (Silver Book) considers and provides guidance for multimorbidity in the context of palliative care. The BMJ Best Practice Comorbidities is an example of guidance provided online to facilitate retrieval of information based on individual backgrounds.

Pre-appraised collections

Pre-appraised evidence summaries (synopses) of systematic reviews and meta-analyses might be used to supplement guideline content with more recent evidence. CareSearch has synopses of evidence in palliative care.

Some other examples of pre-appraised evidence include:

  • BMJ Evidence Based Nursing
    BMJ Evidence-Based Nursing publishes critical commentaries and summaries of selected research in nursing, including reports from other international healthcare journals.
  • Cochrane Library Clinical Answers
    Cochrane Clinical Answers provide a clinically relevant entry point for advising point of care decisions. Each contains a clinical question, a short answer, and data for the outcomes from the Cochrane Review deemed most relevant to practicing healthcare professionals.
  • Health Systems Evidence
    Health Systems Evidence is maintained by McMaster University, Canada to provide a continuously updated repository of syntheses of research evidence. Articles are rated using an appropriate checklist and the database is free to use but registration allows you to view more than 20 results at a time.

  • OT seeker
    An occupational therapy (OT) evidence database including palliative care and providing rating of OT-relevant articles with the PEDro scale.
  • PEDro
    A database of research evaluating the effects of physiotherapy interventions including in the palliative care context. With many of the articles being rated based on the PEDro scale.

Secondary research

Secondary research such as systematic reviews and meta-analyses pool completed research studies to summarise the data and assess whether a significant and consistent outcome is achieved. The CareSearch systematic review collection provides you with easy access to secondary research in palliative care.

Primary studies

Primary studies report findings collected by the authors. These can be qualitative or quantitative studies. In this case the outcomes are relevant to the study group, but you do not know if they can be generalised to others. If the characteristics of the group or person you are caring for are very similar, then it may be relevant to your question.

Use CareSearch PubMed filters or QuickSearch to quickly find primary (and secondary) articles in palliative care.


For background questions, textbooks of validated knowledge are appropriate. For example:

Clinical expertise

Clinical expertise is an important part of EBP where this is combined with patient values and the available evidence when making care decisions. Clinical expertise was defined by Sackett [2] as 'the proficiency and judgment that individual clinicians acquire through clinical experience and clinical practice.'  It will naturally be influenced and limited by the person’s experiences within a population and care context. Generalising this experience to other populations is more difficult and uncertain. An expert panel overcomes some of this bias by combining a range of expertise and experience.

Grey Literature

This includes non-peer reviewed publications such as program or evaluation reports or data sources that are not commercially published. It can be particularly useful as a source of evidence from research or implementation programs that are not published in academic journals. Although the research studies reported in grey literature often use accepted quality approaches it is the lack of peer review by topic experts for validity that places it outside of the evidence pyramid. Search the CareSearch grey literature database.

Web-based retrieval

What about the Internet? Most people will ‘google’ a question, for some it is the first and only place they look. This can be particularly useful to identify grey literature information sources to complement your search of peer reviewed sources. Searches within ‘Google scholar’ can be used to complement searches of literature databases. However, given the range of information available on the internet you need to be cautious. Make sure that the information is current, relevant to your question, from an authority in the field, accurate, and that the purpose of the material is clear.

Evaluating Information Sources

Video from Australian National University Library

Literature databases contain peer-reviewed reports of completed primary and secondary research. These bibliographic databases contain thousands of references from hundreds of different academic journals.

Some literature databases are free and publicly available, while others require payment or subscriptions. You will need to decide on the databases best suited to your research question and then define your search terms. PubMed is one of the best known literature databases in healthcare. It is free to use and up to date.

Some databases specialise in research relevant to professional scope of practice such as nursing, others to a specific study type such as Systematic reviews.

You could also look at journals specialising in palliative care. these will include primary and secondary research articles.

  Example Literature Databases

  • ALOIS a Cochrane database of dementia studies (mostly RCTs, free)
  • CINAHL focuses on literature of relevance to nursing and allied health
  • Ovid’s Medline is a subset of PubMed and specialises in biomedical literature
  • PaPaS Cochrane Systematic Reviews in pain and palliative care (free access)
  • PsycINFO focuses on literature relevant to psychology (including grief and bereavement)
  • PubMed specialises in biomedical literature (free access)
  • TRIP medical database for clinical research evidence (free access)

Once you have defined your search terms you can begin searching your evidence source or chosen database(s). PubMed is one of the most commonly used databases in health care and it is free to use. When combining search terms, you will need to use Boolean logic. These are operator phrases that act as commands when searching.

Boolean operators

There are three basic Boolean search commands: AND, OR and NOT.

  • AND searches find articles containing all search terms.
  • OR searches find articles with one term or the other, or both.
  • NOT eliminates items that contain the specified term (use sparingly to avoid weakening your search).

You can further refine your search terms by:

  • Using quotation marks to search for a phrase e.g. “paediatric palliative care”
  • Using brackets to group terms e.g. (child* or adolescent) AND “palliative care”
  • Using an asterix to indicate a word root e.g. breath* will pick up words built on the root ‘breath’, ie breathing, breathless, breathlessness
  • Using ? or # in place of a possible letter accommodates differences in spelling e.g. pediatric and paediatric will both be picked up if you enter p#ediatric.

Sometimes there is so much literature or such a broad range of literature that you need to apply limits to select the most relevant. In databases such as PubMed you can limit your search by:

  • Time period (e.g. literature from the past 5 years or 12 months)
  • Country of origin (e.g. Australia only)
  • Peer-review status (e.g. only include peer-reviewed literature)
  • Accessibility (e.g. free full text)
  • Language (e.g. only English)
  • Type (e.g. only systematic reviews)

Searching for Evidence

More search tips

Here we provide some additional approaches and considerations that can help you in your search.


When key papers are identified, you can also look for other articles that are ‘similar to’ and/or have ‘cited’ the key paper. Many databases such as PubMed have this as an inbuilt function. It is also useful to scan the reference list of the key papers. Collectively this is known as snowballing, from one or a few key articles you quickly identify many similar or related articles.

Free full text or All Citations? 

Many search engines give you the option of viewing everything in the database or just those research articles that you do not have to pay for, ‘full free text’. If your organisation does not have journal subscriptions, then free text can be helpful because it only shows articles that you can view for free. However, this means your search is biased. You will not see research reports that require payment. Some of these may contain highly relevant and recent evidence that would change your approach to practice changes if you had known about them. Using the CareSearch palliative care filter, ‘free full text’ brings up only 25% of all possible articles relevant to palliative care.

A good approach is to view everything so that you can read the abstracts of all relevant research. Then use ‘free full text’ to see what is easily available. If there are key articles that you do not have access to consider contacting the authors directly for a reprint or purchasing the article. Collaboration with university researchers is a good way to gain access to journal articles. University libraries have subscriptions to a wide range of journals. University researchers are often keen to be involved in applied research. Some public libraries are happy to get research articles for people under inter-library arrangements with universities.

Literature storage

Using software to manage and store the literature helps to keep track of what you have found, as well as assisting with selection and citation of the final references in your synthesis. Commonly used citation management programs include Endnote (requires payment), Zotero, and Mendeley. These import into your computer selected abstracts and publication details of journal articles, reports, books, and other resource types selected within the literature database you are searching. Here they are stored for later use. If you have access to the full text, you can also add a copy to your reference manager.

If you have limited time or lack experience and do not have access to specialist librarians, you may find it more efficient to use a search filter developed by information specialists.

Search filters are experimentally-created, evidence-based, standardised, systematic, subject-based search strategies developed by information specialists. The filter does the hard work for you by providing a search string which pulls relevant literature from within the database. Often these combine keywords and MeSH terms to optimise searching. They also improve search efficiency by including terms and keywords that you may not have thought of, but others have used.

Search filters make it easier to search for specific information. In many respects search filters were an early technology solution to extracting relevant evidence from the very high volumes of published research available.

There are many filters available depending on the topic or study type of interest. There are also checklists available to help you appraise the quality of search filters.

Other search filters

Learn more

Complete the CareSearch learning module Finding Clinical Guidance. This module will explain how the Palliative Care guidelines, clinical Evidence pages, the Systematic Review collection and PubMed searches will assist you to provide better clinical care.

Complete the CareSearch learning module Searching for Evidence. This module focuses on how to search in CareSearch for evidence that can help you to support patients with answers to their questions.

  1. Dicenso A, Bayley L, Haynes RB. Accessing pre-appraised evidence: fine-tuning the 5S model into a 6S model. Evid Based Nurs. 2009 Oct;12(4):99-101. doi: 10.1136/ebn.12.4.99-b.
  2. Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS. Evidence based medicine: what it is and what it isn't. BMJ. 1996 Jan 13;312(7023):71-2. doi: 10.1136/bmj.312.7023.71.

Page created 28 March 2022