Bibliographic databases such as PubMed, Embase and Web of Science, as well as web services from Google to Amazon, employ filters to assist searchers in exploring large sets of search results by specifying particular criteria to view. Common filters in bibliographic databases include publication type, date, language, or study type. In addition, each database or service includes unique filters, based on their particular indexing practice. Filters are an easy and obvious way to view subsets of a broad search.
In this article we will use the example of Article Type PubMed filters within the context of a preliminary topic investigation. It is important to understand what publication type filters represent before getting into specifics of how to use them. Terms or publication characteristics that describe article types include three main categories: publication formats such as journal articles, letters, or newspaper articles; study types such as clinical trials or evaluation studies; and types of organizations that may have funded the research, such as Research Support, Non-U.S. Gov’t.
The filters displayed in the pane on the left side of the search results page are the default options. To get to the complete list of article types, click on the Additional Filters button on the bottom of the filters pane and the full list will appear, including directions for further use.
Each article represents a different depiction, perspective and argument contingent on it being original research, a review, opinion, news piece, or a type of study that contains primary data. We recommend using PubMed Article Type filters to create clusters of the same publication types, which optimizes assessment and evaluation of search results to anyone who is trying to get a deeper understanding of a topic at the onset of a research project.
Considerations
It is important to note that filters are applied only to PubMed records indexed for MEDLINE and therefore using them excludes potentially relevant and useful records from journals not indexed in MEDLINE. We recommend identifying non-MEDLINE records in PubMed and reviewing them separately.
Use of Filter by Task
Below you will find tasks commonly associated with undertaking a preliminary topic investigation, accompanied by the significance of each task. Following each task are suggested filters to aid in your exploratory search, providing some suitable article types for gathering relevant information on your topic.
Gain a topic overview
Gain a topic overview
When exploring the literature on your topic, it is helpful to have an overview of what has already been published on the subject. In addition to original research that may have been done on particular aspects of your topic, various kinds of review articles can help to summarize or synthesize the body of research and often aim to present the current state of knowledge by the researchers producing that work, as well as to anticipate or suggest future research.
Useful Filters:
Review – The review filter will include all publications that aim to examine the published material on a topic, across a range of comprehensiveness. These can include literature reviews, narrative reviews, scoping reviews, systematic reviews, umbrella reviews, meta-analyses, etc. Reading these reviews will inform you how a particular topic has been discussed up to particular point in time and by whom. Reviews can bring to your attention to the key authors in the field and can indicate subtopics that may be of interest or spark new questions related to your research.
Systematic Review – Systematic reviews are a specific type of comprehensive review. Selecting this filter will show only knowledge synthesis articles that follow this very rigorous methodology, often looking at the effectiveness of one intervention compared to another. Systematic reviews are crucial for evidence-based practice and often inform clinical decision-making; therefore reading these reviews can give generalizable information about your topic or population of interest.
Meta-analysis – A meta-analysis is a quantitate method used to combine the results of two or more studies. Sometimes added to a systematic review or published on its own, the results of a meta-analysis may reveal biases, as well as the strengths and weaknesses of the studies included in the analysis. These findings can help you understand the research behind certain treatment recommendations or the results of clinical trials that are relevant to your topic.
Academic Dissertation – Dissertations serve to demonstrate that the author can identify a topic, gather literature, and incorporate that existing knowledge into the development of a new research question. Considering the topic is typically new to the doctoral student doing the work, reading their approach to exploring the literature and reviewing the literature they found will help you get acquainted with the body of knowledge on the topic and suggest ways you yourself can explore it.
Determine that the research is needed
Determine that the research is needed
One purpose of a preliminary topic investigation is to confirm that the research you intend to do will contribute to the field. Sometimes this means doing research into a topic that no one else has tackled; sometimes it is building on the work others have done to advance understanding. Filters can help you in deciding whether to pursue your research project or not. For example, if you intend to conduct a systematic review, you can use the Systematic Review filter to see if the topic you have in mind already exists in that format and how previous researchers have approached the subject.
Useful Filters:
Review, Systematic Review, Meta-analysis – Reading previously published evidence synthesis articles can help you determine if your planned research project fills a gap in the current knowledge. For example, perhaps a significant amount of new research on the topic has been published since the last substantive review was published and a new review is warranted to capture these studies. Or, when appraising the quality of existing reviews, a new review may be needed so that the recognized guidelines are better followed to reduce bias and inaccurate conclusions.
Randomized Controlled Trials – Randomized controlled trials (RCTs) aim to unbiasedly study the efficacy of an intervention through randomly assigning participants to experimental or controlled groups, ideally providing evidence for causality between intervention and outcome. Considerations should be made on the resource intensiveness and potential absence of equipoise when deciding to duplicate efforts.
Clinical Trials – Similar to RCTs, clinical trials aim to determine if treatment, prevention, or behavior approaches are effective. Unlike RCTs, participants of clinical trials are assigned to or sometimes can choose to be in experimental or control groups. Reading published clinical trials can help you determine if the research you are interested in pursuing already exists; in particular, the limitations section of these studies might provide insight on study weaknesses and inform how a future study should be conducted.
Comparative Studies – Comparative studies, through controlling as many conditions as possible (setting, duration, etc.), aim to determine if there are significant differences of predefined measures between or among groups. To not unnecessarily duplicate research, it would be prudent to confirm that a comparative study does not already exist with the same conditions, groups, and predefined measures as your intended research project.
Learn about methodology
Learn about methodology
Research articles and review articles outline the methodologies and approaches previous researchers have employed in conducting their studies. Examining research aligned with your intended methodology provides you with valuable information about how others have addressed the topic and challenges or limitations they may have encountered with their approach. Additionally, consulting published practice guidelines is crucial to understand if there are any standardized procedures or best practices within your field to follow or that you should reference.
Useful Filters:
Publication type you’re pursuing – If you have a particular publication type in mind — case study, clinical trial, systematic review, meta-analysis — you can use that filter to see how others have approached the problem and learn successful techniques as you construct your own study.
Guidelines, Practice Guidelines – Guidelines help improve the efficacy of healthcare by assisting in decision-making. If there are any guidelines published associated with your research topic, reading these will help you to understand what documentation is regulating clinical practice related to your topic, which may inform how you approach your research methods.
Meta-Analysis – Through quantitatively synthesizing the results from the existing literature on a particular topic, meta-analyses often address the shortcomings or problem areas of the research studies they reviewed and make recommendations for how to improve further research, including identifying gaps in current knowledge. Reading these articles can help you learn from the mistakes of others and help you make informed decisions about the methods of your study.
Uncover latest developments
Uncover latest developments
When exploring a research topic it’s important to be acquainted with the various opinions on it and be as current as possible with the latest research.
Useful Filters:
Preprints and Technical Reports – Both of these types of articles will help you understand the latest developments in a research area. Because preprints have not yet entered the publication workflow, they often describe research that has been done very recently. Technical reports, which detail the results of a particular research project, can often shed light on successful and unsuccessful research efforts alike, including the methodology implemented and data obtained.
Address, Editorial, Comment, Letter, and News – The Address, Editorials, Comments, Letters, and News filters provide resources that provide discussions, commentaries, or expert opinions on a particular concept or question. These publications are typically timely and often propose burning questions on a given topic, which can help you in crafting a highly relevant and timely research question.
Find evidence
Find evidence
Collecting data serves to ground your study with facts. These filters provide you with information on datasets and previous studies that may inform your own research.
Useful Filters:
Datasets- Looking at published datasets can help you in articulating the value of your own research by providing the necessary context or evidence uncovered from previous studies. For example, published datasets might provide statistics on your population of interest or present rates of disease transmission that could help inform your own study or could provide evidence that supports your research question.
Government Publications, Legislation, and Legal Cases – These publications are typically the result of evidence-based decision making, in accordance with the Evidence-Based Policymaking Act of 2018. Referring to these documents and looking into the references they cite can ground your research in facts and can provide context to policies that are relevant to your research.
Clinical Studies, Randomized Controlled Trials, Case Reports etc. – The evidence-based research methodologies in these publications often provide useful sources of data that can be used to articulate the potential impact and likely outcomes of a particular intervention.