Lecture 30: Systematic reviews Flashcards
What is the ‘real world’ of finding information for a clinical question?
In the real world…..
* We have a clinical question
* We look for evidence (conduct a review)
* We find a lot of papers that answer our question to some extent
* All are limited to some degree by:
bias, confounding, lack of precision and/or generalizability
* We don’t know what ‘the truth’ is…….
What are the two main types of review?
Narrative review
A narrative review offers a general overview of a topic, summarizing literature without strict methodology. It reflects the author’s perspective and is useful for background information but has a higher risk of bias due to subjective selection.
Systematic review
A systematic review answers a specific research question using a structured, transparent methodology. It involves comprehensive literature searches and minimizes bias, resulting in objective evidence synthesis, often including meta-analysis. This type is valuable for evidence-based practice and policymaking.
Systematic reviews are at the top of the pyramid above RCT’s and are the best technique for determining association
Why are systematic reviews done?
- Collate evidence and synthesize their results
- Done well, systematic review methods reduce bias that may otherwise be encountered with narrative reviews
What are the protocols (methods) of systematic reviews (there are 9)?
Quickly Remember: One Sunny Summer, Everyone Ran Downhill Dancing!”.
1. Question
2. Relevance
3. Objectives
4. Search strategy
5. Selection criteria
6. Eligibility screen
7. Risk of bias
8. Data extraction
9. Data synthesis
What is the question protocol?
PECOT
Example:
What is the effect on body size of a
reduction in sugar intakes in adults?
P- population adults
E- exposure high sugar
C- comparison low sugar
O- outcome body size (obesity)
T- time -“Randomised trials were required to be of at least two weeks’ duration, and prospective cohort studies were required to be of at least one year’s duration.”
What are the relevance and objectives protocol?
Why is it important to do this review?
* Health impacts
* Inform WHO guidelines
Objective statement
* “Objective To summarise evidence on the association between intake of dietary sugars and body weight in
adults and children.”
What is the search strategy protocol?
Example:
* OVID Medline, Embase, PubMed,Cumulative Index to Nursing and Allied Health Literature, Scopus, and
Web of Science electronic databases were searched for clinical trials and cohort studies, published up to
December 2011, which met the inclusion criteria.
- Search terms ……. REPLICABLE AND TRANSPARENT
What is the selection criteria and eligibility screen protocols?
Selection Criteria
Establish explicit inclusion and exclusion criteria for studies to be considered in the review. These criteria are based on factors such as study design, population characteristics, interventions, and outcomes.
ligibility Screen
Conduct an eligibility screening process to assess the identified studies against the selection criteria. This step typically involves reviewing titles, abstracts, and full texts to determine which studies meet the criteria.
What is the risk of bias protocol?
Evaluate the risk of bias in the included studies. This may involve using standardized tools to assess methodological quality, reporting biases, and potential conflicts of interest, which can affect the validity of the results.
What is Meta analysis?
Meta-analysis is a statistical technique that combines results from multiple studies to obtain a pooled estimate of effect, enhancing the overall power and precision of findings. It helps to identify patterns, strengths, and inconsistencies in the data.
Makes the diamond thing
What are the Data extraction and synthesis stage of the protocol?
Data Extraction
Extract relevant data from the included studies systematically. This includes key information on study characteristics, participant demographics, interventions, outcomes, and results, often using standardized forms.
Data Synthesis
Synthesize the extracted data to summarize findings across studies. This can involve qualitative synthesis or quantitative methods, such as meta-analysis, to compare results and draw conclusions regarding the research question.
META ANALYSIS important
What is Heterogeneity in a study?
when something varies across different groups it is heterogeneous
What is homogeneity in a study?
when something is consistent across different groups it is homogeneous
What are the challenges and advantages of a meta analysis?
Challenges
* Doing all steps well
* Publication bias
* Poor quality trials/ studies
* Heterogeneity
Can lead to….
* Conflicting reviews
* Inconclusive results
Advantages:
* Reproducibility, rigour
* Comprehensive
* Transparent limits
* Gaps in knowledge
* Basis for decisions
The final stage of systematic review is interpretation, what are the steps/processes for this?
- Principal findings (answer PECOT)
- Limitations to the evidence - RISK OF BIAS
- Implications
- for clinical Practice
- for further Research
Publication bias
Rubbish in, rubbish out (bias in studies may prevent a meta analysis)
