Umbrella Review – A Paradigm Shift in Health Science Research Methodology

In health science, conducting research work is highly essential to frame new therapeutic and diagnostic guidelines. As a result, research publications have made a tremendous growth. Although there is numerous research methodology framework are available to evaluate the quality of final evidence, still there is a lacune existing to conclude with final conclusion. Always there is a quest for the invention of new research methodology which ultimately resulted in birth of a new concept called “Umbrella Review.” Hence, the purpose of this research publication is to enlighten about the literature pertaining to umbrella review which is greatly required in the field of health science and represents a pinnacle in the hierarchy of evidence-based literature.

Keywords: Keywords: Health science research, Research methodology, Umbrella review, Systematic review, Meta-analysis

In the current scenario tremendous research is happening not only in technical field but also in health science. As a result, published research work is popping like hot cakes worldwide, with intention to provide full depth information on a numerous topic [1,2]. As we all know currently meta-analysis and systematic reviews are most commonly used to evaluate the clinical and epidemiological questions of interest. However, some-times it becomes essential to examine the same research not just by evaluating the single question of interest but has to evaluate many different questions on the same research work [1,2].

There is a quest for the solution or new research methodology which solves the overflow, robust surge of research evidence in the medical science. A new methodology which objectively collects and summarizes the already published research evidence on the given topics to compare and evaluate the final evidence is none other than what the research named is Umbrella Review. In simpler terms we can say it is a useful tool for conducting a rapid review on any research topic title with a broad area [3]. Therefore, the purpose of this research paper is to discuss in detail regarding definition, synonyms, advantages, disadvantages, its scope, challenges and about methodology to conduct Umbrella Review [4].

Definition

According Cochrane data base, an umbrella review can be defined as ‘systematic reviews of previous one, which provide an overall assessment of the information available on a specific topic.’ Whereas Ioannidis in 2009, defined it as ‘systematic collections and assessments of multiple systematic reviews and meta-analysis done on a specific research topic.’ In 2016, Booth defined it as “a cluster of existing systematic reviews on a shared topic. Based on Grant and Booth definition given in 2009, umbrella review is a “overarching review” that “aggregate findings from several reviews that address specific questions [4-6].

Synonyms

The concept behind Umbrella review is totally new, concrete and relatively unexplored. Literature shows various nomenclatures given by different authors to describe umbrella reviews such as ‘overviews of reviews,’ ‘synthesis of reviews,’ ‘summaries of systematic reviews,’ ‘umbrella reviews’ and ‘reviews of reviews.’ Choi and Kang [1] referred it as “Umbrella Review” as metaphorically this review methodology enable researcher to synthesize and evaluate the evidence peering at the water streaking under the umbrella under the pouring rain of evidence.

Goal of Umbrella Review

The main goal of an Umbrella Review is not to repeat the assessment of risk bias or meta-analysis from included reviews or assessment of study eligibility or searches but rather to provide an overall picture of findings for particular questions as mentioned below. In simpler term the aim of an UR is not to re-synthesize the original articles or included reviews by meta-analysis but it includes the following items [7].

• Comparison of one treatment versus multiple treatment
• Investigation of the same intervention and condition but with different outcomes
• Analyses of different interventions for the same condition

The requirement to conduct an Umbrella Review depends on total number of available quality systematic reviews and meta-analysis in the literature. The outcome of Umbrella Review will be outstanding when multiple SRMAs have already been conducted on a specific research topic. If very few numbers of SRMAs are available on the given topic, it is wise to conduct more and more new relevant SRMAs to contribute more information to the topic rather than conducting Umbrella Review. Moreover, it is also worth to conduct new SRMAs to polish already existing and outdated multiple SRMAs, but not performing the Umbrella Review using those multiple, outdated SRMAs which is not at all concluding the research question in a proper way [8].

Umbrella Review summarizes information gathered from multiple overview articles and makes it easier to review the evidence and permits comparison of study results between each of the individual reviews. Umbrella Review focuses on a single broader question compared to a typical review which addresses multiple different treatment comparisons instead of focusing on only one [8].

Merits and demerits of Umbrella Review

Although Umbrella Review represent the highest level of evidence currently available in research field of medicine compared to other systematic methodologies, it too has advantages and disadvantages. It is mainly useful for developing guidelines and clinical practice, and also useful for comparing competing interventions.

Merits of Umbrella review [9,10]

• It provides an overall picture of study quality, study sizes, uncertainty, hints of bias and heterogeneity among well-defined broad research group.
• It points out the gaps and limitations in a specific research area and can give clues or suggestions for conducting further research.
• It conserves valuable research resources by avoiding vast literature search using scratch as it utilizes the advantage of already done and existing systematic reviews.
• It compares results between different investigations or epidemiological survey thereby depicting a detailed picture regarding the limitations and strength of the interventions.
• It provides a comprehensive view of multiple investigations for a specific medical condition or multiple epidemiological associations including either a specific risk factor or a specific medical condition.

 Demerits of Umbrella Review [9,10]

• It does not provide information for epidemiological associations or interventions that have not been studied in systematic reviews or meta-analyses.
• The final quality of Umbrella review depends directly on the validity of the systematic reviews and meta-analyses being investigated.
• The problems and biases which exist in primary studies could not be clarified or compounded during Umbrella review process.
• It suffers from a lack of quality or lack of sufficient data of the studies and reviews included in systematic reviews or meta-analyses.

Challenges associated with Umbrella Review [4,6,8,9]

Researcher can encounter potential challenges while performing umbrella Review. Although it is not possible to cross check all the original studies to confirm whether all the data collected in SRMAs is correct, sometimes researcher need to go through the original publications once again to collect additional information like number of cases, sample size and epidemiological evidence to obtain standard results and also to assess the criteria for strength of the evidence.  If the primary studies and SRMAs have done properly covering entirely the topic of question, then UR will subsequently conducted in standard way with no gaps or Luke holes seen in the investigation. Therefore, the validity of Umbrella review ultimately depends on the final quality of both the primary studies and SRMAs. Suppose if the data found negative or scanty in the primary studies, or SRMAs, the author need to re-search for the original articles to remove errors.  Moreover, the eligibility criteria required for umbrella review may not be present or may be deviated in the SRMAs. For instance, if Umbrella review aims to concentrate only on randomised trials as study focus, the SRMAs might also contain additional observational studies which is not required for conducting umbrella review and those studies should be separated [4,5]. Therefore, while conducting an UR, researcher should keep in mind the specific eligibility criteria which should specifically match with clinical question.  Author needs to repeat the statistical analyses to analyse all the relevant features regarding heterogeneity between studies, 95% prediction intervals and other statistical biases. It is also essential to grade the evidence according to a set of criteria and discuss various other potential biases. Other challenges associated with umbrella review which need further attention are dealing explicitly with potential primary study, using MeSH terms in search methodology, detail description about data extraction process and presentation of all essential information from primary studies and systematic reviews which are considered for the review [6-9].

Research working group structure for writing Umbrella Review protocol

Joanna Briggs Institute formulated a new research methodology working group in 2013, to propose or write a protocol of Umbrella Review in order to show how this new research methodology is carried out. This working group included four types of participants like researchers, clinicians, systematic review authors and journal editors. Four countries such as the USA, Australia, Thailand and Canada were involved in this research methodology workshop [9].

Steps or methodology in conducting Umbrella Review [9]

Any Umbrella Review which needs to be conducted in health research should include a peer-reviewed protocol, articulated question (s), detailed inclusion criteria, a well-structured search methodology to identify and select relevant existing reviews, proper methods for critical appraisal of selected reviews and finally includes process of data extraction and methods for summarizing and presentation of the data obtained (Table 1).

Table 1: Key Steps in writing Umbrella Review

Umbrella reviews provide a bird eye view by summarizing information available from multiple overview articles including systematic review articles and meta-analysis and make easier to review the evidence and facilitates comparison of results between each of the individual reviews. Therefore, they represent a pinnacle in the hierarchy of highest level of evidence in modern research methodology pertaining to health medicine research.