Research:

 

NHMRC levels of evidence:

I

Systematic review

II

Proper RCT

III-1

Pseudo RCT

III-2

Comparative study with concurrent control

-Cohort study

-Case-control study

III-3

Comparative study without concurrent control

IV

Case series

V

Case report

 

NHMRC grades of recommendation:

A

Excellent

·      Many good trials

·      Guides practice

B

Good

·      Couple of good trials

·      Guides practice in most situations

C

Satisfactory

·      Couple of ok trials

·      Careful with application

D

Poor

·      Low quality trials

·      Beware application

 

Trial phases:

Phase

Numbers

Purpose

0

10-20

Kinetics

1

20-100

Safety + dose finding

2

100-300

Safety + efficacy

3

1k-2k

Safety + efficacy

4

Many

Safety + efficacy

 

Types of Bias

Type

Explanation

Mitigation

Hawthorne effect

Being studied = feel good

Control group

Sampling bias

Study participants are not reflective of the population

Appropriate inclusion and exclusion criteria

Selection

Intervention and control groups are not the same

Randomisation

Performance

Unequal care between groups

Identical care except for intervention vs control

Attrition

Unequal withdrawal between groups

Impossible to overcome

Reporting

Some findings reported, others not

 

Response

Questions encourage a certain type of answer

Control group

Recall

Patient reports symptoms differently depending upon allocation

Patient blinding

Detection

Intervention and control group assessed differently

Assessor blinding

Pre-defined criteria

Observer

Data collector able to be subjective about the outcome

Assessor blinding

Hard outcomes

Publication

Negative results don’t get published

Clinical trial registries

 

Meta-analysis:

Definitions

·      Narrative review: pick and choose according to your world view

·      Systematic review: combined systematic analysis of multiple studies

·      Meta-analysis: combined quantitative analysis of multiple studies

Stages

·      Define inclusion and exclusion criteria

·      Search for trials

·      Assess heterogeneity

·      Perform meta-analysis

·      Assess whether result makes sense

Forest plot

= what’s the outcome?

·      X axis: odds ratio

·      Y axis: individual studies

·      Dot size: weight

·      Line width: confidence intervals

·      Diamond centre: point estimate

·      Diamond width: confidence interval

Funnel plot

= is there publication bias?

·      Large studies should cluster around the true effect

·      Publication bias is suspected if results cluster on one side of the plot

Pros

·      Statistical power

·      Generalisability

Cons

·      Whether to combine apples and oranges

·      How to combine apples and oranges

Interpretation

·      Negative result -> probably accept

·      Positive result -> probably do a large RCT to confirm

 

Retrospective studies

Indications

·      Long latency

·      Rare outcome

·      Unethical intervention

·      Unethical to wait

Process

e.g. case-case control study

·      Generate hypothesis: exposure -> outcome

·      Find patients with exposure

·      Find patients with no exposure

·      Match them in as many ways as possible

·      Calculate odds ratio

 

Critical appraisal of a paper:

 

ANZCA version:

Introduction

·      Appropriate question

·      Appropriate study design

·      Appropriate endpoint

Research methods

·      Measurement techniques

·      Who, where, when, how many, how long for

·      Control group, randomization, blinding

·      Inclusion and exclusion criteria

Result

·      Answers the question?

·      Statistically significant?

·      Presented clearly?

·      Missing data and why?

Discussion & conclusion

·      Logical?

·      Biased?

Summary

·      Quality?

·      Relevance?

·      Changes my practice?

 

Simple version:

Intro

Why did they bother?

·      Original?

·      Incremental?

·      Significant?

Method

Did they do it properly?

·      Right subjects?

·      Right intervention?

·      Right outcome of interest?

Result

What did they find?

·      What is the result?

·      Is it statistically significant?

·      Is it clinically significant?

·      If positive, why? (positive IRL, or confounder?)

·      If negative, why? (negative IRL, or underpowered?)

·      If fancy statistics, why?

·      If missing patients, why?

Implication

What does this mean?

·      Does this change what I think? (balance of evidence)

·      Does this change what I should do? (patient population)

·      Does this change what I could do? (feasibility)

 

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