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Advanced literature search and systematic reviews

An introduction to systematic reviews

Formulate your question

Formulating a clear, well-defined, relevant and answerable research question is essential to finding the best evidence for your topic. On this page we outline the approaches to developing a research question that can be used as the basis for a review. 

Using frameworks to structure your question

Frameworks have been designed to help you structure research questions and identify the main concepts you want to focus on. Your topic may not fit perfectly into one of the frameworks listed on this page, but just using part of a framework can be sufficient.

The framework you should use depends on the type of question you will be researching.

Type of research question  Framework Disciplines
Clinical questions PICO (variants: PIO, PICOT, PICOS) Health
Quantitative  PEO, PICO (variants: PIO, PICOT, PICOS) Health; Social Sciences; Business and Policy; Environment
Qualitative PEO, PICo, CLIP, ECLIPSE, SPICE, SPIDER Social Sciences; Management; Health
Mixed methods SPICE, SPIDER Health; Social Sciences
Methodological or theoretical  BeHEMoTH Health

Selecting a framework

A framework used for formulating a clinical research question, i.e. questions covering the effectiveness of an intervention, treatment, etc. 

Example: Are mind body therapies a viable alternative to prescription drugs to control headaches in children?
PICO element Definition Scenario
P (Patient / Population / Problem) Describe your patient, population or problem


I (Intervention / Indicator) What intervention is being considered? Mind body therapies
C (Comparison / Control) What is your comparison or control? Prescription drugs
O (Outcome) What outcome are you looking for?  Controlling headaches

Extensions to PICO

If your topic has additional concepts, there are extensions to the PICO framework that you can use: 

PICOS - S stands for study design. Use this framework if you are only interested in examining specific designs of study. 

PICOT - T stands for timeframe. Use this framework if your outcomes need to be measured in a certain amount of time, e.g. 24 hours after surgery. 

PICOC - C stands for context. Use this framework if you are focussing on a particular organisation or circumstances or scenario. 

A framework used for questions relating to prognosis issues. 

Example: How likely are children with febrile seizures to develop a seizure disorder?
PFO element Definition Scenario
P (Population) Who is the question focussed on? Children 
F (Prognostic Factors) What is being prognosed? Febrile seizures
O (Seizure disorders) What are the possible outcomes? Seizure disorders 

A framework used for questions relating to the prevalence / incidence of a condition.

Example: What is the prevalence of claustrophobia in adult patients undergoing MRI?
CoCoPop element Definition Scenario
Co (Condition) What condition / problem are you examining? Claustrophobia
Co (Context) In which context is your question set? MRI
Pop (Population) Describe your population Adults 

Used for questions relating to cost effectiveness, economic evaluations and service improvements.

Example: Ways of improving health visiting services to elderly in rural communities.
CLIP element Definition Scenario
C (Client) Who is the service aimed at? Elderly
L (Location) Where is the service located? Rural communities
I (Improvement) What do you want to find out? How the services can be improved
P (Professional) Who is involved in providing the service? Health visiting

Used for questions relating to cost effectiveness, economic evaluations, and service improvements.

Example: Retention of A&E nurses in the NHS.
ECLIPSE element Definition Scenario
E (Expectation) Purpose of the study - what are you trying to achieve? To find retention rates
C (Client group) Who is the information needed for? Patients? Managers?
L (Location) Where is the client group based? NHS
I (Impact) If your research is looking for service improvement, what is it? How is it measured? Retention of staff
P (Professionals) What professional staff are involved? Nurses
S (Service) For which service are you looking for information? A&E

Used for qualitative questions evaluating experiences and meaningfulness 

Example: What are the experiences of patients with pressure sores who receive treatment at home?
PICo element Definition Scenario
P (Patient / Population / Problem) Describe your patient, population, or problem Patients with pressure sores
I (Interest) Describe the event, experience, activity or process Experiences / views / opinions
Co (Context) Describe the setting or characteristics  Care in the home

For quantitative and qualitative questions evaluating experiences, and meaningfulness.

Example: The quality of life of carers for people with dementia.
PEO element Definition Scenario
P (Patient / Population / Problem) Describe your patient, population or problem Carers
E (Exposure) What is the issue you are interested in? Dementia
O (Outcomes or themes) What (in relation to the issue) do you want to examine? Quality of life

Used for qualitative questions evaluating experiences and meaningfulness.

Example: Attitudes of carers of people with dementia towards reminiscence therapy.
SPICE element Definition Scenario
S (Setting) Where is the study set? United Kingdom? Care homes?
P (Population / Perspective) From which population / perspective is the study done? Carers
I (Intervention) Describe the intervention being studied Reminiscence therapy
C (Comparison) Is the intervention being compared with another? Not available
E (Evaluation) How well did the intervention work? Attitudes

Framework used for qualitative questions evaluating experiences and meaningfulness.

Example: What are young parents experiences of attending ante-natal education?
SPIDER element Definition Scenario
S (Sample) Describe the group you are focussing on Young parents
PI (Phenomenon of interest) The behaviour or experience your research is examining Ante-natal education classes
D (Design) How was the research carried out?  Interview, questionnaire, phenomenology
E (Evaluation) Which outcome are you measuring? Experiences
R (Research type) Qualitative? Quantitative? Or mixed methods? Qualitative

Inclusion and exclusion criteria

When you formulate a research question you also need to consider your inclusion and exclusion criteria. These are a list of pre-defined characteristics the literature must have, if they are to be included in a study. Different factors can be used as inclusion or exclusion criteria. 

The most common inclusion / exclusion criteria are: 

Geographic location

Limit the review of study to geographical area.


How far back do you wish to search for information? (For systematic reviews you need to give a reason if you choose to restrict your search by date).

Publication type

Common excluded publications are reviews and editorials.


Adults, child studies, certain age groups?


Limit the review of study to language.

Peer review

Has to be reviewed by accredited professionals in the field.

Study design

Randomised controlled trials, cohort studies?


Primary care, hospitals, general practice, schools?

The scoping search

Once you have a clear research question, you need to conduct a scoping search to identify:

  • The search terms you should use to retrieve information on your topic.
  • The body of the literature that has already been written on your topic.
  • If a systematic review, covering the question you are considering, has already been published or has been registered and it is in the process of being completed. If that is the case, you need to modify your research question. If the systematic review was completed over five years ago, you can perform an update of the same question. 

Search the following resources to find systematic reviews, either completed or in progress. Check the Supporting videos and online tutorials page on this guide for demonstration of how to do a scoping search. 

To find primary research related to your topic you can search databases available via: