systematic literature review dr elena antonova. lecture aims types of literature reviews what is a...
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Systematic Literature Review Dr Elena Antonova Slide 2 Lecture aims Types of literature reviews What is a systematic literature review Why do we need them How to be systematic about it avoiding this state: Slide 3 Learning outcomes Clarity about the purpose of lit review Understanding of the lit search process Appreciation of a systematic approach Ability to conduct a lit review Slide 4 Publication food chain Anecdotal Expert opinion Case reports Case-control studies Cohort studies Randomised controlled trials Reviews and meta-analyses Slide 5 Types of reviews Systematic reviews: Use explicit and rigorous methods to identify, critically appraise, and synthesize relevant studies Narrative reviews: Summaries of research that lack explicit descriptions of systematic methods Meta-analysis: quantitative review using statistical analyses Meta-ethnography: systematic review of qualitative data Slide 6 Mulrow (1994) on systematic lit review: Through critical exploration, evaluation, and synthesis the systematic review separates the insignificant, unsound, or redundant deadwood in the medical literature from the salient and critical studies that are worthy of reflection Slide 7 What is systematic about it? Key search words Searching method Criteria for including/excluding references Clear structure in appraising the evidence Explicit discussion of limitations Slide 8 Why a systematic literature review? Ecclectism and the rise of BPS psychiatry: proliferation of treatment approaches growing number of RCTs published limited NHS resources -> need to identify effective evaluations to guide research investments and health care provision Slide 9 Archie Cochrane 1909-1988 1972 Effectiveness and Efficiency: Random Reflections on Health Services Emphasised the necessity of RCT studies It is surely a great criticism of our profession that we have not organised a critical summary, by specialty or subspecialty, adapted periodically, of all relevant randomised controlled trials The beginning Slide 10 Established in 1993 www.cochrane.orgwww.cochrane.org International, non-profit, independent organisation Promotes evidence of the effects of therapies Production and dissemination of systematic reviews There are > 11,500 people working within The Cochrane Collaboration in over 90 countries. 50% are authors of Cochrane Reviews Cochrane Collaboration Slide 11 Another quote from Archie: I had considerable freedom of clinical choice of therapy: my trouble was that I did not know which to use and when. I would gladly have sacrificed my freedom for a little knowledge. I had never heard then of 'randomised controlled trials', but I knew there was no real evidence that anything we had to offer had any effect on tuberculosis, and I was afraid that I shortened the lives of some of my friends by unnecessary intervention." Slide 12 Who needs literature reviews? Over two million!!! articles are published annually in the biomedical literature in over 20 000 journals. High quality information is not always available to everyone. -> impossible for health care providers, researchers, and policy makers to keep up to date. Slide 13 How is it helpful? Reduces large quantities of information to palatable pieces for digestion Minimises bias: systematic reviews and meta-analyses apply explicit scientific principles aimed at reducing random and systematic errors of bias Integrates up-to-date, reliable and critical biomedical information for use by: Practitioners: research-based practice Decision and policy makers Researchers (to avoid reinventing the wheel) Slide 14 Further advantages of systematic reviews Assess consistency of relationships and effects Among studies of the same or similar interventions Across populations and settings Across different diseases Establish generalisability of scientific findings Identify variables affecting generalisability and consistency (e.g. sex, age, ethnicity) Facilitate the translation of medical research discoveries to clinical practice Slide 15 How is it helpful to you? To locate previous studies in your subject area To find effective research methodologies To see if (and, if so, how well) your research topic has been tackled previously To put your research in the context of other work in this field To establish relevance To support bids for funding and sponsorship Slide 16 The literature Slide 17 Before entering the maze Formulate your question! Pragmatic, well-focused questions Need to know what we are asking, in order to know what studies we include in the review. Slide 18 Stage 1: literature search Slide 19 Key words Not too broad (scope creep) Not too narrow (empty net) Think of all possibly synonyms Check already retrieved papers for possible key words and their combinations Make sure to follow the search engines rules in combining the key words Slide 20 Databases PsychInfo (APAs database) MedLine/PubMed Scopus: scientific, technical, medical and social sciences Google Scholar But Google definitely rocks! Slide 21 Determining the year Generally, start with the year not included in the last literature review of the field If no previous reviews, go by when the first relevant study was published If overlapping, but not identical topic of review, ok to use the same studies Slide 22 Literature Search Tree Initial key word search Retrieved papers cited by others Retrieved papers references search Unpublished data search ( literature, phd thesis, societal meetings) Slide 23 Document you search in a detailed and explicit way Atkins et al 2008 Slide 24 Stage 2: selecting papers Slide 25 Method of selecting Decide on your inclusion/exclusion criteria This might depend on how advanced is the field (e.g. no-control studies, open-blind trials vs. RCTs) What demographics of participants might influence outcomes? (e.g. age, sex, ethnicity) Slide 26 Details of all studies included in review Slide 27 Slide 28 The write up Title Introduction Method Results Discussion Conclusion References Slide 29 Introduction Introduce the field of research State the question to be addressed Make reference to the previous reviews of the field Make clear why further review is need (i.e. number of new papers) Introduce any competing models/theories that the review aims to appraise Slide 30 Introduction: specific points How important is the problem? Prevalence, incidence and impact of illness Is there any uncertainty about how to deal with the problem? What is the intervention supposed to achieve? What is the anticipated outcome of the intervention What are the models of efficacy of the intervention? Slide 31 Method: design & procedures Describe : Search criteria and method Selection criteria, including explicit justification for study exclusion The scales or checklist by which studies are appraised Any techniques of synthesis or analysis by which they are presented Slide 32 Method: design & procedures Tabulate : - inclusion criteria - sample size - baseline patient characteristics - withdrawal rate - results of primary and secondary end points (for longitudinal studies) Slide 33 Method Define participants Define interventions Define comparisons Define outcomes Slide 34 Participants How is the disease/condition defined? What are the most important characteristics that describe the participants relevant to your review? Are there any relevant demographic factors? (e.g. age, sex, ethnicity) What is the setting? (e.g. hospital, community etc) Who should make the diagnosis? Are there any co-morbidities to be excluded? Are there any other types of people who should be excluded from your review (because they are likely to react to the intervention in a different way)? How will studies involving only a subset of relevant participants be handled? Slide 35 Interventions What are the experimental and control (comparator) interventions of interest? Does the intervention have variations (eg dosage, mode of delivery, personnel who deliver it, frequency of delivery, duration of delivery, timing of delivery)? Are all variations to be included (for example is there a critical dose below which the intervention may not be clinically appropriate)? How will trials including only part of the intervention be handled? How will trials including the intervention of interest combined with another intervention (co-intervention) be handled? Slide 36 Comparisons What are you interested in comparing the intervention to? Depends on the primary question of the review: Are you only interested in whether the intervention offers benefit over the natural course of the disorder (ie a comparison to placebo or no treatment) or are you interested in whether the intervention offers benefit over other interventions. Slide 37 Outcome measures How do you think it is important to measure change with respect to this intervention in this population? List all the outcomes you are including in your review. Primary and Secondary Consider outcomes relevant to all potential decision- makers, including economic data. Should cover beneficial and adverse effects Slide 38 Have a method to your method Reproducibility Ideally the transparency of methods used should mean that another researcher addressing the same question will identify the same set of studies and arrive at the same overall conclusion. Slide 39 Results Normally the largest section of your write up Aim for a systematic grouping of the studies, e.g. results of controlled vs no-control trials, open- blind vs double-blind, or some other criteria Slide 40 Practical tips Use a method which suits you best: brief summary of each study for your notes map the labs and their studies !Make sure you know the labs and their stories! Have a story to tell, not just summaries Slide 41 Discussion & Conclusions Summaries the main results Appraise the results (power, generasibility) Clinical significance Appraise in relation to the models/theories of phenomenon (e.g. d