Why Are Systematic Reviews Important for Evidence Based Practice

• Journal List
• J Family unit Med Prim Care
• v.2(1); January-Mar 2013
• PMC3894019

J Family Med Prim Care. 2013 Jan-Mar; ii(1): 9–xiv.

Systematic Reviews and Meta-analysis: Agreement the Best Evidence in Primary Healthcare

S. Gopalakrishnan

Department of Community Medicine, SRM Medical College, Hospital and Inquiry Centre, Kattankulathur, Tamil Nadu, Republic of india

P. Ganeshkumar

Department of Community Medicine, SRM Medical Higher, Infirmary and Inquiry Middle, Kattankulathur, Tamil Nadu, Republic of india

Abstract

Healthcare decisions for individual patients and for public health policies should be informed by the all-time available inquiry testify. The exercise of evidence-based medicine is the integration of individual clinical expertise with the best available external clinical prove from systematic inquiry and patient's values and expectations. Primary intendance physicians demand bear witness for both clinical practice and for public health determination making. The testify comes from good reviews which is a land-of-the-art synthesis of electric current evidence on a given enquiry question. Given the explosion of medical literature, and the fact that time is always scarce, review articles play a vital office in conclusion making in evidence-based medical practice. Given that most clinicians and public health professionals practise not take the time to rail downwardly all the original articles, critically read them, and obtain the bear witness they need for their questions, systematic reviews and clinical practice guidelines may be their best source of prove. Systematic reviews aim to identify, evaluate, and summarize the findings of all relevant individual studies over a health-related issue, thereby making the available show more accessible to decision makers. The objective of this commodity is to introduce the master care physicians about the concept of systematic reviews and meta-assay, outlining why they are important, describing their methods and terminologies used, and thereby helping them with the skills to recognize and understand a reliable review which volition be helpful for their twenty-four hours-to-day clinical practice and research activities.

Keywords: Evidence-based medicine, meta-analysis, main care, systematic review

Introduction

Evidence-based healthcare is the integration of best inquiry evidence with clinical expertise and patient values. Green denotes, "Using evidence from reliable research, to inform healthcare decisions, has the potential to ensure best exercise and reduce variations in healthcare delivery." However, incorporating enquiry into practice is fourth dimension consuming, and then we demand methods of facilitating piece of cake access to evidence for busy clinicians.[1] Ganeshkumar et al. mentioned that nearly half of the private practitioners in Bharat were consulting more than four h per day in a locality,[2] which explains the difficulty of them in spending time in searching evidence during consultation. Ideally, clinical decision making ought to be based on the latest evidence available. However, to keep abreast with the continuously increasing number of publications in health research, a primary healthcare professional would demand to read an insurmountable number of articles every mean solar day, covered in more than 13 1000000 references and over 4800 biomedical and health journals in Medline alone. With the view to address this challenge, the systematic review method was developed. Systematic reviews aim to inform and facilitate this process through research synthesis of multiple studies, enabling increased and efficient admission to show.[1,3,four]

Systematic reviews and meta-analyses have become increasingly important in healthcare settings. Clinicians read them to go along up-to-date with their field and they are oft used as a starting point for developing clinical practice guidelines. Granting agencies may crave a systematic review to ensure there is justification for further research and some healthcare journals are moving in this direction.[5]

This article is intended to provide an easy guide to understand the concept of systematic reviews and meta-analysis, which has been prepared with the aim of chapters building for general practitioners and other primary healthcare professionals in research methodology and day-to-day clinical practice.

The purpose of this commodity is to introduce readers to:

1. The two approaches of evaluating all the bachelor bear witness on an upshot i.due east., systematic reviews and meta-analysis,

2. Talk over the steps in doing a systematic review,

3. Innovate the terms used in systematic reviews and meta-assay,

4. Interpret results of a meta-assay, and

5. The advantages and disadvantages of systematic review and meta-analysis.

Awarding

What is the effect of antiviral treatment in dengue fever? Most often a master care physician needs to know convincing answers to questions like this in a primary care setting.

To detect out the solutions or answers to a clinical question like this, 1 has to refer textbooks, inquire a colleague, or search electronic database for reports of clinical trials. Doctors need reliable information on such issues and on the effectiveness of large number of therapeutic interventions, but the information sources are too many, i.e., nearly 20,000 journals publishing 2 million articles per year with unclear or confusing results. Considering no written report, regardless of its type, should be interpreted in isolation, a systematic review is generally the best form of evidence.[6] So, the preferred method is a good summary of enquiry reports, i.e., systematic reviews and meta-analysis, which volition give evidence-based answers to clinical situations.

At that place are ii fundamental categories of research: Primary research and secondary inquiry. Main enquiry is collecting data straight from patients or population, while secondary research is the analysis of data already nerveless through main inquiry. A review is an article that summarizes a number of master studies and may draw conclusions on the topic of involvement which can be traditional (unsystematic) or systematic.

Terminologies

Systematic review

A systematic review is a summary of the medical literature that uses explicit and reproducible methods to systematically search, critically appraise, and synthesize on a specific issue. It synthesizes the results of multiple main studies related to each other by using strategies that reduce biases and random errors.[seven] To this cease, systematic reviews may or may non include a statistical synthesis called meta-assay, depending on whether the studies are similar enough so that combining their results is meaningful.[eight] Systematic reviews are often called overviews.

The evidence-based practitioner, David Sackett, defines the post-obit terminologies.[3]

• Review: The general term for all attempts to synthesize the results and conclusions of 2 or more publications on a given topic.

• Overview: When a review strives to comprehensively identify and track down all the literature on a given topic (likewise called "systematic literature review").

• Meta-analysis: A specific statistical strategy for assembling the results of several studies into a single guess.

Systematic reviews adhere to a strict scientific design based on explicit, pre-specified, and reproducible methods. Considering of this, when carried out well, they provide reliable estimates nearly the effects of interventions and so that conclusions are defensible. Systematic reviews tin also demonstrate where knowledge is lacking. This can so be used to guide hereafter research. Systematic reviews are usually carried out in the areas of clinical tests (diagnostic, screening, and prognostic), public wellness interventions, adverse (harm) furnishings, economic (price) evaluations, and how and why interventions work.[9]

Cochrane reviews

Cochrane reviews are systematic reviews undertaken by members of the Cochrane Collaboration which is an international not-for-profit organization that aims to help people to make well-informed decisions most healthcare by preparing, maintaining, and promoting the accessibility of systematic reviews of the effects of healthcare interventions.

Cochrane Primary Health Intendance Field is a systematic review of primary healthcare enquiry on prevention, handling, rehabilitation, and diagnostic test accuracy. The overall aim and mission of the Primary Wellness Care Field is to promote the quality, quantity, dissemination, accessibility, applicability, and touch on of Cochrane systematic reviews relevant to people who work in primary care and to ensure proper representation in the interests of primary intendance clinicians and consumers in Cochrane reviews and review groups, and in other entities. This field would serve to coordinate and promote the mission of the Cochrane Collaboration inside the primary healthcare disciplines, equally well equally ensuring that primary care perspectives are adequately represented within the Collaboration.[10]

Meta-analysis

A meta-analysis is the combination of data from several independent master studies that accost the same question to produce a single estimate like the effect of handling or risk factor. Information technology is the statistical assay of a big collection of analysis and results from individual studies for the purpose of integrating the findings.[11] The term meta-analysis has been used to announce the total range of quantitative methods for research reviews.[12] Meta-analyses are studies of studies.[thirteen] Meta-analysis provides a logical framework to a enquiry review where similar measures from comparable studies are listed systematically and the available effect measures are combined wherever possible.[fourteen]

The cardinal rationale of meta-analysis is that it reduces the quantity of data past summarizing data from multiple resources and helps to plan inquiry as well as to frame guidelines. It also helps to make efficient utilize of existing data, ensuring generalizability, helping to check consistency of relationships, explaining data inconsistency, and quantifies the data. It helps to ameliorate the precision in estimating the gamble by using explicit methods.

Therefore, "systematic review" volition refer to the entire process of collecting, reviewing, and presenting all available evidence, while the term "meta-analysis" will refer to the statistical technique involved in extracting and combining data to produce a summary outcome.[fifteen]

Steps in doing systematic reviews/meta-analysis

Following are the six primal essential steps while doing systematic review and meta-analysis.[16]

Define the question

This is the most important part of systematic reviews/meta-analysis. The research question for the systematic reviews may be related to a major public wellness problem or a controversial clinical situation which requires adequate intervention as a possible solution to the present healthcare need of the community. This step is most important since the remaining steps will be based on this.

Reviewing the literature

This can exist done past going through scientific resources such as electronic database, controlled clinical trials registers, other biomedical databases, not-English literatures, "grey literatures" (thesis, internal reports, non–peer-reviewed journals, pharmaceutical manufacture files), references listed in primary sources, raw data from published trials and other unpublished sources known to experts in the field. Among the available electronic scientific database, the popular ones are PUBMED, MEDLINE, and EMBASE.

Sift the studies to select relevant ones

To select the relevant studies from the searches, we need to sift through the studies thus identified. The start sift is pre-screening, i.e., to determine which studies to retrieve in full, and the second sift is selection which is to look again at these studies and make up one's mind which are to be included in the review. The next step is selecting the eligible studies based on similar written report designs, year of publication, language, option among multiple articles, sample size or follow-up issues, similarity of exposure, and or treatment and completeness of information.

Information technology is necessary to ensure that the sifting includes all relevant studies like the unpublished studies (desk drawer problem), studies which came with negative conclusions or were published in non-English journals, and studies with modest sample size.

Assess the quality of studies

The steps undertaken in evaluating the study quality are early definition of report quality and criteria, setting upward a skillful scoring arrangement, developing a standard form for assessment, computing quality for each study, and finally using this for sensitivity assay.

For example, the quality of a randomized controlled trial can be assessed past finding out the answers to the following questions:

1. Was the assignment to the treatment groups really random?

2. Was the treatment allocation concealed?

3. Were the groups similar at baseline in terms of prognostic factors?

4. Were the eligibility criteria specified?

5. Were the assessors, the care provider, and the patient blinded?

6. Were the point estimates and measure out of variability presented for the principal outcome mensurate?

7. Did the analyses include intention-to-treat analysis?

Summate the outcome measures of each study and combine them

Nosotros need a standard measure of upshot which tin can be applied to each report on the footing of its upshot size. Based on their type of outcome, following are the measures of result: Studies with binary outcomes (cured/not cured) have odds ratio, gamble ratio; studies with continuous outcomes (blood force per unit area) have means, difference in ways, standardized divergence in ways (event sizes); and survival or time-to-event information have hazard ratios.

Combining studies

Homogeneity of different studies can exist estimated at a glance from a woods plot (explained below). For instance, if the lower confidence interval of every trial is below the upper of all the others, i.east., the lines all overlap to some extent, then the trials are homogeneous. If some lines do not overlap at all, these trials may be said to be heterogeneous.

The definitive test for assessing the heterogeneity of studies is a variant of Chi-square exam (Mantel–Haenszel test). The final footstep is calculating the common estimate and its conviction interval with the original information or with the summary statistics from all the studies. The best gauge of treatment effect tin exist derived from the weighted summary statistics of all studies which volition be based on weighting to sample size, standard errors, and other summary statistics. Log scale is used to combine the data to gauge the weighting.

Translate results: Graph

The results of a meta-analysis are commonly presented as a graph called forest plot considering the typical forest plots appear equally forest of lines. It provides a simple visual presentation of individual studies that went into the meta-analysis at a glance. It shows the variation betwixt the studies and an guess of the overall result of all the studies together.

Forest plot

Meta-analysis graphs can principally be divided into half-dozen columns [Effigy i]. Individual study results are displayed in rows. The offset column ("written report") lists the individual written report IDs included in the meta-analysis; normally the start author and year are displayed. The second column relates to the intervention groups and the third column to the control groups. The quaternary cavalcade visually displays the study results. The line in the middle is chosen "the line of no effect." The weight (in %) in the 5th column indicates the weighting or influence of the study on the overall results of the meta-analysis of all included studies. The higher the percentage weight, the bigger the box, the more than influence the report has on the overall results. The sixth column gives the numerical results for each study (due east.g., odds ratio or relative risk and 95% confidence interval), which are identical to the graphical display in the fourth column. The diamond in the final row of the graph illustrates the overall outcome of the meta-analysis.[4]

Interpretation of meta-assay[iv]

Thus, the horizontal lines represent individual studies. Length of line is the conviction interval (usually 95%), squares on the line represent effect size (risk ratio) for the study, with area of the square being the study size (proportional to weight given) and position as point judge (relative hazard) of the study.[7]

For example, the wood plot of the effectiveness of dexamethasone compared with placebo in preventing the recurrence of acute severe migraine headache in adults is shown in Figure two.[17]

Forest plot of the effectiveness of dexamethasone compared with placebo in preventing the recurrence of astute severe migraine headache in adults[17]

The overall consequence is shown as diamond where the position toward the center represents pooled point estimate, the width represents estimated 95% confidence interval for all studies, and the blackness patently line vertically in the eye of plot is the "line of no effect" (e.m., relative risk = 1).

Therefore, when examining the results of a systematic reviews/meta-analysis, the following questions should be kept in heed:

1. Were apples combined with oranges?

   • Heterogeneity among studies may make whatsoever pooled estimate meaningless.

2. Were all of the apples rotten?

   • The quality of a meta-analysis cannot exist whatsoever ameliorate than the quality of the studies it is summarizing.

3. Were some apples left on the tree?

   • An incomplete search of the literature tin bias the findings of a meta-analysis.

4. Did the pile of apples amount to more than just a loma of beans?

   • Make sure that the meta-analysis quantifies the size of the upshot in units that yous can sympathize.

Subgroup analysis and sensitivity analysis

Subgroup analysis looks at the results of dissimilar subgroups of trials, e.yard., by considering trials on adults and children separately. This should exist planned at the protocol stage itself which is based on good scientific reasoning and is to be kept to a minimum.

Sensitivity analysis is used to determine how results of a systematic review/meta-analysis modify by fiddling with data, for example, what is the implication if the exclusion criteria or excluded unpublished studies or weightings are assigned differently. Thus, later on the assay, if irresolute makes footling or no difference to the overall results, the reviewer's conclusions are robust. If the key findings disappear, so the conclusions need to be expressed more than cautiously.

Advantages of Systematic Reviews

Systematic reviews have specific advantages because of using explicit methods which limit bias, draw reliable and accurate conclusions, hands evangelize required information to healthcare providers, researchers, and policymakers, help to reduce the fourth dimension filibuster in the research discoveries to implementation, ameliorate the generalizability and consistency of results, generation of new hypotheses most subgroups of the study population, and overall they increment precision of the results.[xviii]

Limitations in Systematic Reviews/Meta-analysis

Equally with all research, the value of a systematic review depends on what was washed, what was plant, and the clarity of reporting. Equally with other publications, the reporting quality of systematic reviews varies, limiting readers' power to assess the strengths and weaknesses of those reviews.[v]

Even though systematic review and meta-assay are considered the best evidence for getting a definitive answer to a research question, there are certain inherent flaws associated with it, such as the location and option of studies, heterogeneity, loss of information on important outcomes, inappropriate subgroup analyses, disharmonize with new experimental information, and duplication of publication.

Publication Bias

Publication bias results in information technology beingness easier to find studies with a "positive" effect.[nineteen] This occurs especially due to inappropriate sifting of the studies where there is ever a tendency towards the studies with positive (significant) outcomes. This effect occurs more unremarkably in systematic reviews/meta-assay which demand to be eliminated.

The quality of reporting of systematic reviews is still not optimal. In a recent review of 300 systematic reviews, few authors reported assessing possible publication bias fifty-fifty though there is overwhelming evidence both for its existence and its impact on the results of systematic reviews. Even when the possibility of publication bias is assessed, there is no guarantee that systematic reviewers take assessed or interpreted it appropriately.[twenty]

To overcome sure limitations mentioned above, the Cochrane reviews are currently reported in a format where at the end of every review, findings are summarized in the author's indicate of view and as well give an overall moving picture of the result by means of plain linguistic communication summary. This is found to be much helpful to understand the existing evidence about the topic more than easily past the reader.

Summary

A systematic review is an overview of primary studies which contains an explicit statement of objectives, materials, and methods, and has been conducted according to explicit and reproducible methodology. A meta-analysis is a mathematical synthesis of the results of two or more main studies that addressed the same hypothesis in the same way. Although meta-assay can increase the precision of a upshot, it is important to ensure that the methods used for the reviews were valid and reliable.

Loftier-quality systematic reviews and meta-analyses accept great care to discover all relevant studies, critically assess each study, synthesize the findings from private studies in an unbiased manner, and present balanced important summary of findings with due consideration of whatsoever flaws in the evidence. Systematic review and meta-assay is a fashion of summarizing inquiry evidence, which is generally the best class of evidence, and hence positioned at the top of the hierarchy of evidence.

Systematic reviews tin can be very useful determination-making tools for primary care/family unit physicians. They considerately summarize big amounts of information, identifying gaps in medical research, and identifying beneficial or harmful interventions which will be useful for clinicians, researchers, and even for public and policymakers.

Footnotes

Source of Support: Nil

Disharmonize of Interest: None declared.

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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3894019/

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