Step 2: Access the information
Once you have converted your clinical query into an answerable clinical question, you can start finding and acquiring research evidence that could be useful to addressing your clinical question.
Before you begin searching for information it is important to consider the following:
- What types of evidence are you searching for?
- Where can you find specific types of evidence?
- How to search databases for evidence?
What types of evidence are you searching for?
When searching for evidence to address a clinical question, it is important to understand the levels of quality research evidence is available in. It's considered best practice to first search for the highest quality of evidence as this ensures that the information used in decision-making processes is reliable, accurate, and based on rigorous research methods. High-quality evidence is less prone to bias and provides more trustworthy conclusions compared to lower-quality evidence.
The Haynes' Hierarchy of Evidence, developed by Canadian professor of medicine and clinical epidemiologist, Dr. Brian Haynes, sorts various types of resources into tiers based on their quality of evidence. While it is weighted heavily towards intervention-type questions, it remains broadly applicable to other question types.
Pre-appraised secondary sources are materials that have been critically evaluated and summarised by experts in a field. These sources, such as review articles, meta-analyses, and evidence-based practice guidelines, review original studies to provide researchers and practitioners with trustworthy insights, saving time and effort in accessing credible information.
Original studies provide valuable up-to-date and detailed research, but haven't already been appraised. Different original studies are best suited to support different types of foreground questions. It's important to know which original studies are best suited to addressing which types of foreground questions.
Any resource found by a researcher should be read carefully and evaluated to ensure it is suitable for addressing the specific clinical question.
Click on the plus (+) icons below to learn about the tiers in Haynes' Hierarchy of Evidence:
"H5P - Levels of Evidence Pyramid" by Deakin Library is licensed under CC BY-NC 4.0 / Adapted from Of studies, syntheses, synopses, summaries, and systems: the “5S” evolution of information services for evidence-based healthcare decisions by Brian Haynes
Activity overview
This interactive image hotspot provides information on the Haynes' Hierarchy of Evidence. Each hotspot explores a different tier Haynes' Hierarchy of Evidence. Hotspots are displayed as plus (+) icons that can be clicked, to present information a tier from Haynes' Hierarchy of Evidence.
Top tier: Systems or Computerised Decision Support Systems (CDSS)
The top of the pyramid is evidence-based clinical information systems, also known as Computerised Decision Support Systems (CDSS).
These systems match best practice evidence to a patient record. These systems are not common yet. So, you would need to start your research at the tier below, Summaries.
Second tier: Summaries
Summaries contain evidence that has been summarised and synthesised from reviews and studies. Summaries are strong resources when developing your research.
Clinical practice guidelines (known as point-of-care tools) fall under the Summaries tier. Developed from evidence in current literature (including critical appraisal) they can provide:
- recommendations for specific clinical questions
- considerations on the benefits and harms of alternative actions
- considerations on individual patient preferences
- incorporate clinical opinion
In Australia, many healthcare settings have developed clinical practice guidelines. Such as the Cancer Council, the Heart Foundation, and the Royal Children’s Hospital. Point-of-care tools are included in subscription-based resources such as BMJ Best Practice and Uptodate.
Third tier: Synopses of syntheses
Synopses of syntheses collects and summarises findings from high quality systematic reviews.
Synopses of syntheses often provide reasonable information to support a clinical intervention. They can be found in journals, such as the Evidence-based Nursing.
Fourth tier: Syntheses
Syntheses is an exhaustive review of original studies on a focused topic. The most common type of review is a systematic review.
A systematic review is when a researcher forms a research question on a topic. Identifies relevant studies to the research question. Assesses the quality of relevant studies and collects their findings. Evidence from findings is then evaluated either by quantitative synthesis (e.g. meta-analysis) or by other means. This allows the researcher to draw conclusions on their research question, based on the synthesised findings.
Systematic reviews are found in databases such as the Joanna Briggs Institute, Cochrane Library, Medline or CINAHL.
Fifth tear: Synopses of studies
Synopses of studies are critically appraised brief summaries of original studies. Evidence from a collection of original studies is summarised by an expert in the field.
Be aware that this type of resource is considered less reliable than a systematic review. As the evidence may not have the most up to date information on a particular topic. You may need to find the latest information from original research studies.
Sixth tier: Studies
Studies provide valuable up-to-date and detailed research, compared to pre-appraised resources. Studies useful for cross-checking the original source in a guideline or evidence summary.
As studies are original, they’ve not been pre-appraised. Studies need to be evaluated, to determine if they contain quality evidence to address a research question.
Types of studies fall into sub-tiers based on the quality of evidence:
- Randomized Controlled Trails (RCT)
- Cohort studies
- Case controlled studies
- Cross-sectional studies
- Case series, case reports or case studies
CINAHL or Medline are useful databases for finding studies.
Seventh tier: Randomized Controlled Trials (RCTs)
Randomized Controlled Trials (RCTs) are considered the highest quality of study. RCTs provide the strongest evidence, due to their methodology. In RCTs, participants are randomly allocated into two, or more groups. Each group receives a different intervention. RCTs end with the results of the effects of the different interventions are measured and collected. The results lead to conclusions about whether a particular intervention is more effective than another.
RCTs are useful in addressing Intervention questions.
Eighth tier: Cohort studies
Cohort Studies are longitudinal and observational studies. Participants who have been exposed to a particular risk factor are followed over a period of time. During that time, they're compared to another group that wasn't exposed to a particular risk factor. Participants are observed to determine whether disease does or doesn't develop. They may also be observed to determine how a particular disease progresses.
Cohort studies are useful in addressing Etiology and Prognosis questions.
Ninth tier: Case controlled studies
Case controlled studies compares people with a condition to those without. The study explores a person's whole life, with the help of medical records and a person's memory. To identify factors that might relate to the condition.
Case controlled studies are less reliable than RCTs or cohort studies. This is due to cause and effect not necessarily set up in case-controlled studies.
Case controlled studies are useful in addressing Etiology questions.
Tenth tier: Cross-sectional studies
Cross-sectional studies observe a disease or condition, along with other related factors at a specific point in time for a given population (known as a "snapshot").
A cross-sectional study might research a snapshot and then follow it up with one or more snapshots at later points in time. This is known as a repeated cross-sectional data analysis.
Cross-sectional studies are useful in addressing Frequency questions.
Eleventh tier: Case Series, case report or case study
A case report or case study is on the treatment of an individual patient. They have no statistical quality because there is no control group for comparison. When there is many case reports or case studies, this is known as a case series.
The individual nature of these studies limits the ability to draw conclusions and apply them to a wider population.
Case series, case reports, or case studies provide some insights into Frequency questions, but often lead to inquiries requiring higher-level study designs.
Bottom tier: Background Information or Expert Opinion
The lowest quality of evidence is background information and expert opinions, anecdotes, or editorials. When beginning your research, these types of resources can provide useful discussion around a topic. However, they're not considered to be scientific evidence.
Note
This guide focuses on the Haynes hierarchy of evidence. However, other hierarchy of evidence models exist. For example, the Johns Hopkins Evidence-Based Practice hierarchy is a widely used model in nursing and healthcare contexts.
Where can you find specific types of evidence?
Databases are useful places to find specific types of evidence to address your clinical question.
Check out the table below to identify which databases contain the types of evidence appropriate for addressing your clinical question.
| Database | Summaries | Synopses of syntheses | Syntheses | Synopses of studies | Studies |
|---|---|---|---|---|---|
| BMJ Best Practice |  |
||||
| Campbell Collaboration Library of Systematic Reviews | |
||||
| ClinicalKey | |
|
|
|
|
| Cochrane Library | |
|
|
||
| Medline Complete | |
|
|
|
|
| MJA Clinical Guidelines | |
||||
| National Clinical Guidelines Clearinghouse | |
||||
| NHMRC Clinical Practice Guidelines Portal | |
||||
| NICE Clinical Guidelines | |
||||
| PubMed | |
|
|
|
|
| Therapeutic Guidelines | |
||||
| TRIP | |
|
|
|
|
| UpToDate | |
How to search databases for evidence?
Once you have identified the appropriate databases, it’s time create a search strategy to find relevant evidence/information to address your clinical question.
A search strategy is combination of the key elements of your clinical question and search techniques (e.g., synonyms, truncation, phrase searching, and Boolean operators).
Click on the plus (+) icons below to see how search techniques can be applied to key elements of a clinical question to develop a search strategy.
Activity overview
This interactive activity shows an image of the Library advanced search bars filled in with an example search as follows:
adolescent* OR teen* OR "young adult*"
AND regional* OR remote OR farm*
AND "nicotine replacement therap*" OR NRT
AND counselling OR "cognitive behavioural therap*"
There are 4 selectable icons that explain each of the search techniques used in this advanced search.
Technique 1: Alternative keywords (synonyms)
When searching databases, it’s important to think about synonyms, other words that have the same meaning as your keywords.
In this example, alternative words for a young person would be adolescent, teen or young adult.
Technique 2: Truncation
Often synonyms are based on a similar root word with a different ending. Applying a symbol, such as an asterisk (*), at the end of a keyword includes additional words with different endings and spellings.
In this example, farm* will find farms, farmer, farming, farmland, farmyard, etc.
Technique 3: Phrase searching
Databases typically search for words individually. To make sure that they search for keywords as a phrase, apply a symbol such as a double quotation marks (" "), at the beginning and end of the keyword phrase.
In this example, "nicotine replacement therap*" will find results containing these words in this exact phrase and not find results that contain these words individually.
Technique 4: Boolean operators
Boolean operators use capitalised words (such as AND, OR, NOT) to produce more relevant results, when searching in a database.
Using AND between words finds results containing those words.
Using OR between words finds results containing any of those words.
Using NOT before a word excludes results containing that word.
Note
For further information on developing a search strategy for a database, check out the Finding evidence for your health assessment.