Lectures 14: Introduction to critical appraisal and how to read published papers

Question 1

What is critical appraisal?

Answer 1

 The process of systematically examining research evidence to assess its validity, results and relevance before using it to inform a decision  Essential part of evidence-based clinical practice, allowing us to make sense of research evidence and begin to close the gaps between research and practice

Question 2

List some factors to consider when doing critical appraisal?

Answer 2

 Question: Is there a hypothesis? Is the question relevant?  Design: Is it cross-sectional, cohort, case-control, ecological, RCT? Hierarchy of studies. Is it appropriate?  Population: Sample size. Are results generalisable to other populations  Methods: Exposure measurements, interview, measure, questionnaire etc.  Analysis: Appropriate statistical tests. Chance? Confounding?  Confounders: Presence of any confounders and attempts to  exclude or adjust  Bias: Measurement/Selection?  Ethics: Is the study ethical?  Interpretation: Do the authors interpret correctly? Do they make a causal inference? Bradford-Hill?

Question 3

State the hierachy of study?

Answer 3

add pic

Question 4

List the heirachy of study design?

Answer 4

Question 5

What would be the ideal design for a therapuetic method?

If you want to know wetaher a drug is more effecitve than another drug?

If you want to know weather a drug works?

Answer 5

RCT- Randomised control setting

Question 6

What would be the ideal design for a diagnosis method?

Is it better to have a mamogram or remove a lump and have a biopsy

Answer 6

In a cross-sectional study, data are collected on the whole study population at a single point in time to examine the relationship between disease (or other health related state) and other variables of interest.

Cross-sectional studies therefore provide a snapshot of the frequency of a disease or other health related characteristics in a population at a given point in time.

Question 7

What would be the ideal design for a screening?

Answer 7

Cross sectional Study

In a cross-sectional study, data are collected on the whole study population at a single point in time to examine the relationship between disease (or other health related state) and other variables of interest.

Cross-sectional studies therefore provide a snapshot of the frequency of a disease or other health related characteristics in a population at a given point in time.

Question 8

What would be the ideal design for a prognosis?

Answer 8

Longitudinal cohort study

Cohort Study = a prospective study in which individuals are selected on the basis of EXPOSURE STATUS and are followed over a period of time to allow the frequency of occurrence of the outcome of interest in the exposed and non exposed groups to be compared. i.e. take a group of people, note whether they’ve been exposed or not, observe them over time and see who gets ill and who doesn’t. This type of study typically produces a RELATIVE RISK

NOTE: PEOPLE IN COHORT STUDIES DON’T HAVE THE DISEASE BEING INVESTIGATED

They are followed to see who will get the disease

Question 9

What is a case control study?

Answer 9

Case Control Study = a retrospective study in which individuals are selected on the basis of WHETHER OR NOT THEY HAVE THE OUTCOME OF INTEREST. Exposure status is explored to establish whether the exposure is more common in those who have the outcome or the control. This type of study always results in ODDS RATIO - for example, comparing the odds of being exposed in those who had the outcome with those who didn’t (the control)

NOTE: PEOPLE IN CASE CONTROL STUDIES ALREADY HAVE THE DISEASE BEING INVESTIGATED

It investigates the relationship between a risk factor and one or more outcomes

Case (people who have the outcome) Control (people who don’t have the outcome) Study

Question 10

What is an ideal study for a causation: environmental, lifestyle ect factors and their impact on health?

Answer 10

cohort or case control study