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Finding Information: Systematic Searches for Health

Introduction to Systematic Searches for Health

This guide is designed to help you complete a systematic literature search for literature in health subjects. You will most likely have to complete a search in this way for research methods modules and your dissertation. Please note that this is a general guide; you should always check in with your course team, supervisor, and assignment documentation to clarify aims and expectations. 

As well as being a large component of your assignment or dissertation, systematic searches of this kind...

“Are becoming ever more important in health and social care. The growing importance of evidence-based practice (EBP) within health and social care today has led to literature reviews becoming more relevant to current practice."  Aveyard, H. (2023) Doing a literature review in health and social care: a practical guide. 5th edn. London: Open University Press.

Features of a Systematic Search in Health

A systematic search for health has some similar components to a general literature search, but there are a few things that are done differently. This is because in order to be a rigorous research method, the search needs to be carried out and presented in a systematic and thorough way. 

For example, in your dissertation, you may need to include elements such as: 

  • PEO/PICO table 
  • Inclusion/exclusion criteria 
  • Search table 
  • PRISMA flow chart 

All of these elements, along with your commentary on the search, provides a clear picture of how you planned and executed your search. Importantly, the search table in particular allows your search to be replicable by others. 

Doing Your Systematic Search


This section gives a breakdown of the steps you will need to take in order to complete the search process. It can be helpful to break the process down in this way so you can see what is needed and tackle it one step at a time.

However, the search process is not always this straightforward: it is an iterative process. Don't be disheartened if you move back and forth through the steps before you finalise your search and choose your final articles. For a more detailed description of the search process see our guide here

Complete the below task to consolidate your understanding. 

Scope the Literature

Background or scoping searches are preliminary searches of the literature for information surrounding your topic before you start your structured, systematic literature search. It can help you to gain an understanding of the topic, look at what literature is available, and think about what keywords you might use in your final search. 

To get more information about how to do a background (or scoping) search, see our guidance here. 

You can use your background search to narrow down your topic. For example, you may have a general topic that you are interested in. When you start to explore the literature, recurring themes may appear. You could use one or more of these themes to focus and refine your question.

Formulate Your Question

After you have done a background search and got a better idea of your research topic, you will need to translate it into a  question. Tools which you can help you to formulate your question include the PICO and PEO frameworks.

The PEO and PICO frameworks are used widely in nursing and health research and in professional practice. They are strongly advocated by the NHS. They help you to formulate an answerable question and to identify the key concepts within it. They also help you to develop your inclusion and exclusion criteria and you should refer back to these when you are making your final selection of articles. 

Which framework you choose will depend on the nature of your question. Generally, PEO is used for qualitative questions and PICO for quantitative ones. Look at the descriptions below for more information on each. 


The PEO framework lends itself more to qualitative research. 

Population/ Patient/ Problem   Who are the users - patients, family, practitioners or community being affected? What are the symptoms, condition, health status, age, gender, and ethnicity? What is the setting e.g. acute care, community, mental health?
Exposure   Exposure to a condition or illness, a risk factor, screening, rehabilitation, service etc.
Outcomes or themes Experiences, attitudes, feelings, improvement in condition, mobility, responsiveness to treatment, care, quality of life or daily living.

Example question: 

What are the attitudes of health professionals towards caring for older patients with dementia in an acute setting?

P Health professionals working in an acute setting
E Caring for older patients with dementia 
O Attitudes of health professionals’ towards older dementia patients


PICO is mainly used for quantitative research and allows for comparison between interventions. 

Population/ Patient/ Problem Who are the users - patients, family, practitioners or community being affected? What are the symptoms, condition, health status, age, gender, and ethnicity? What is the setting e.g. acute care, community, mental health?
Intervention  Pharmacological (e.g. a drug) or non-pharmacological (e.g. therapy, screening, surgery, service or test).
Comparison  This element involves identifying an alternative or comparison intervention, if applicable. It could be a different drug, therapy, placebo, standard treatment, or any other relevant comparison.
Outcome What is to be achieved, changed or measured? It could be a clinical outcome, such as improvement in symptoms, mortality rates, quality of life, or any other measurable outcome.

Example question: 

How effective are pressure garments in the treatment of leg ulcers?

P Patients with leg ulcers
I Pressure garments 
C Not applicable
O Usefulness in the treatment of leg ulcers 

Test your knowledge of PICO and PEO with the quick quiz below. For each example, pick whether you think you would use PICO or PEO as your chosen framework. 

Develop Your Search Terms

Now you can start to construct your search strings. Search strings are made up of keywords from your question with alternative terms as appropriate. Look at our guide on generating keywords and alternative terms for more information.

Remember, search terms represent the main concepts from your question. While they will be grounded in PICO/PEO, they do not need to follow exactly the same structure as PEO/PICO - this can result in poor and inconsistent results.

Test your knowledge with the below activity. 

You have formulated a question and PICO table. You now need to construct your search strings. Which of the following would you choose, and why?

How does the administration of antibiotics pre-hospital affect mortality rates for patients with sepsis? 

P: patients with suspected sepsis in the pre-hospital setting

I: pre-hospital antibiotics 

O: impact on mortality rates 


Apply Search Techniques

Once you have decided on your search terms, you will combine them using Boolean Operators. You may also wish to utilise additional advanced search techniques like truncation, phrase searching, wildcards, and proximity search. See our Enhancing Your Search guide for further guidance

Click on the image below to see where search techniques have been added to improve this search.

Select Your Databases

When researching your dissertation, you are expected to search across multiple databases (usually three). To learn more about our database collection, click here. Be sure to confirm the exact number by taking a look at your course handbook, corresponding with your course team, or having a chat with your supervisor. 

Go to the A-Z of eResources to find out what databases are available in your discipline. Filter by your subject area and then look through the list. Each database will have a description of what is included. Use this to help you decide which ones to try. 

You will notice that the layout of the databases can vary slightly. Below are a few videos showing how to search in a few of the most-used databases. 

Refine Your Results

Once you are happy with your search strings and have tried them out in a database, it is very likely that you will need to refine your results in some way. What you need to do next will depend on the results you end up with. For example, do you have too many results? Too few? Are they relevant to your topic? 

Explore the below pages to decide whether your sources are appropriate, and how you might refine them further, then have a look at the information below next steps: 

How many results should I have? 

This is a very common question, without an exact answer.

You need enough relevant articles to have a little choice in what you select, but not so many that you're overwhelmed. The aim is to be able to look through at least the title and ideally the abstract of every article in your result list. This allows you to select your articles in a systematic and informed way. Can you realistically do this? If not, consult the links above to help you refine your result set. 

Select Your Articles

By now you have completed your search in your chosen database(s). You’ve refined the results and are happy with the number and relevance. Be sure to read through our guidance on Selecting your Sources if you need a little more help with refining your results. 

Now it’s time to select your final set of articles for your review. This number will vary widely depending on your assignment, level, and course of study. Confirm how many papers you need with your course team, supervisor, or by checking your course handbook.

Inclusion and Exclusion Criteria 

You must select and exclude articles based on recorded inclusion and exclusion criteria. 

  • Inclusion criteria are predefined characteristics or criteria used to determine which studies should be included in a research synthesis process. They help ensure that selected studies align with the research question and objectives, and they typically include factors such as study population, interventions, outcomes, and study design.
  • Exclusion criteria in literature searching are predefined characteristics or criteria used to identify and exclude studies that do not meet specific requirements from a research synthesis process. These criteria help researchers exclude studies that may introduce bias or lack relevance to the research question, improving the quality and focus of the synthesis.

You will determine your inclusion and exclusion criteria based on the parameters of your topic and PEO/PICO table. You will produce a table with two columns detailing your inclusion and exclusion criteria, which will be included in your final dissertation. You may also use your inclusion and exclusion criteria to help you produce a PRISMA flow diagram. 

See the activity below for an example and to test your knowledge. 


Present Your Search Results

One element of your systematic search which is specific to health subjects is the presentation of your search strings and results in a table. This makes it clear what you have searched for and where, what limits you applied and how many results you ended up with. Your search table makes your search process clear and replicable to anyone reading your assignment or dissertation. 

You should complete the final version of this table at the end of the search once you are completely happy with it and are confident that you have an appropriate number of relevant results. 

To complete your search table, you will need to follow the below steps: 

  1. Search each individual string on its own in each of your selected databases. Record the number of search results for each string and database. 
  2. Search all strings in combination in each of your selected databases. Record the number of search results for each database. 
  3. Apply equivalent filters in each of your selected databases. Record the number of search results for each database. 

Not sure how to present your search table? Download the files below. 

What next? 

Well done! You’ve completed your systematic search and presented your results in a table. What next? 

In addition to the search information (PICO/PEO, search table, inclusion and exclusion criteria) you will often need to present information about how you selected your articles from the final set of results (PRISMA Flow Diagram) and then include a critique of the articles (CASP/Holland and Rees). A brief introduction to both of these is included below. 



A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow chart is a diagram that depicts the flow of information through the different phases of your systematic search. It shows the number of records identified, included, and excluded, and the reasons for exclusions.

The PRISMA flow chart has different boxes and arrows that connect them. The boxes show the different steps, like finding studies, screening them, and deciding which ones to include or exclude. The arrows show how many studies are involved at each step. The flow chart is important because it helps you show how you chose the studies and if there were any problems or biases in the process.
More information and examples can be found on the PRISMA website.

Critiquing frameworks

Always check with your tutor or supervisor as to whether they have a preference for a particular framework. Here are two that are commonly used. 


The Critical Appraisal Skills Programme (CASP) tool helps people evaluate research papers in healthcare. It uses a step-by-step approach and asks questions about things like how the study was done and what the results mean. By using CASP, you can figure out if a study is reliable and can be used to make decisions. 

More information, examples and template CASP checklists can be found on their website.

Holland and Rees

Another available framework is from Holland and Rees' book Nursing: Evidence-based practice skills (linked below). 

Their frameworks for critiquing quantitative or qualitative articles can be found here. 

More information can be found by looking at the book. Follow the link below to see its availability in the library.