Systematic Reviews and Meta Analysis Flashcards Preview

Y1 Fwong Epidemiology > Systematic Reviews and Meta Analysis > Flashcards

Flashcards in Systematic Reviews and Meta Analysis Deck (10)
Loading flashcards...
1

How are systematic reviews related to EBM?

EBM is when you make clinical decisions based on three factors:
1) Your PERSONAL clinical judgement
2) Available evidence around you
3) Patient's preferences/values

For 2), there are so many scientific journal articles available around you, and each year more and more journals are being published. You don't have time to look at all these papers individually and so you can look at systematic reviews which 'sums up' a lot of papers that are quite similar/ are related to each other

2

What are systematic reviews?

Review of all the evidence available concerning a CLEARLY FORMULATED QUESTION.
Systematic and explicit methods are used to:
1) identify and select relevant sources that are related and could be potentially useful to answer your question
2) critically appraise relevant research
3) collect data from theses studies
4) analyse data from the studies that are included in the review

3

Why do you conduct a systematic review? (i.e. what is its purpose?)

DATA QUANTITY is increasing exponentially each year. You need a way to keep up with this increasing amount of information as you are unlikely going to have time to look at each individual journal. Therefore, you look at systematic reviews which tries to answer a specific question, using evidence collected from other papers. This in a way acts as a 'summary'

DATA QUALITY
Individual studies may not be reliable on their own because e.g. they may be only focusing on one subset of the population and so may not be representative. Each individual paper may also have their own limitations (poor study design, low power study etc) which therefore affects data quality. By looking at multiple studies, it can help to counteract these problems

4

What is involved in a systematic review? (3 stages). This is a long answer question, write down your answer and then compare

1) Stage I: Planning a Review
○ Form a question that you want to answer, decide on inclusion and exclusion criteria (to help you decide which papers to use and not use)
○ Usually framed around PICOS:
§ Population- who u studying?
§ Intervention/Comparison- what drugs are you testing?
§ Outcomes- What outcomes are you looking for in the papers that you look at? e.g. side effects of drugs
§ Study Design- what study designs are you looking for in the papers e.g. you are only looking at randomised controlled trials?

2) Stage II: Conducting the Review
a. Identification of research – This requires clearly defined search criteria and a thorough search of all published literature (including exhaustive searches of reference lists, conference proceedings and contact with researchers in the field).

b. Selection of which studies to use using exclusion and inclusion criteria decided in stage I
c. Study Quality Assessment-assess quality of the paper using recognised or user defined criteria (user defined means its decided by the person doing the systematic review)
d. META-ANALYSIS
§ The use of statistical techniques in a systematic review to integrate the results of included studies.

3) Stage III: Reporting and Dissemination
Basically presenting data collected from all the studies e.g. in table or more commonly, a FOREST PLOT.

May also analyse the data

5

What is meta analysis

The use of statistical techniques in a systematic review to integrate the results of included studies

6

How is meta analysis done?

Meta analysis is the use of statistical techniques in a systematic review to integrate the results of included studies.

Large studies are given more weight than smaller studies as large studies are more reliable. This is all u need to know, no need to go into the details of equations etc

7

limitations of systematic reviews and meta analyses?

Publication bias - only a small subset of data may be available to the person doing the systematic review. Eg. French journals may not be included on pubmed and so you will not be able to find them on pubmed. This leads to loss of data, so BIAS

Inconsistency of results (heterogeneity):
studies differ on e.g. population studied, type of intervention, healthcare system etc

Low study quality

8

Advantages of systematic reviews and meta analyses?

Generate a pooled overall risk estimate

Produce a more reliable and precise estimate of effect

Explore differences (heterogeneity) between published studies.

Identify whether publication bias is occurring.

9

What is a funnel plot and what is it used for?

A plot that gives you a visual representation of whether or not there could be publication bias/small study bias. Symmetrical= no bias, asymmetrical=bias

10

What do you need to consider when critically appraising a systematic review and meta analysis?

Look at powerpoint by Dr Frederick B Piel "More on study design" slides 41 and 42