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DEN2025 - Dental Public Health and Behavioural Science > Study Designs > Flashcards

Study Designs Flashcards

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1
Q

Why is study design important?

A

Study design defines the way in which the data on the health status of interest is measured, collected and analysed

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2
Q

Name 4 important factors to consider when designing a study

A
  1. Question you wish to answer
  2. Availability of data
  3. Sampling methods / Data collection
  4. Cost of design
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3
Q

What are 2 main types of study design?

A
  1. Observational

2. Experimental

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4
Q

What are observational studies used for?

A

Monitor or describe the health status of a population

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5
Q

What are experimental studies used for?

A

Examine the effect of an intervention on the outcome of interest

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6
Q

What is the hierarchy of evidence?

A

Gives an indication of the quality of evidence, reflecting reliability and validity of various forms of evidence

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7
Q

Name 3 examples of weak studies in the hierarchy of evidence

A
  1. Ideas / Opinions
  2. Case series
  3. Ecological studies
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8
Q

Name 3 examples of strong studies in the hierarchy of evidence

A
  1. Systematic reviews / Meta analysis
  2. Randomised controlled trials
  3. Cohort studies
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9
Q

What are the 2 most useful designs in observational studies?

A
  1. Cohort study

22. Case-control study

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10
Q

Name 3 weak designs of observational studies

A
  1. Case reports
  2. Cross-sectional studies
  3. Ecological studies
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11
Q

Describe the relationship between causation and observational study

A

Causation cannot be inferred solely from the results of observational study

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12
Q

Describe an example of possible confounding by other variables during an observational study

A
  • A study of whether smoking of cigarettes causes oral cancer
  • Must take into account of confounding by drinking alcohol
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13
Q

Describe a cohort study

A
  • Starts by defining a subgroup of the population to follow-up over a period of time
  • Exposures in the participants are measured at outset of study
  • Disease experience during follow-up is recorded
  • In the form of epidemiological studies, it is usual to form categories
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14
Q

Describe a case-control study

A
  • Starts by identifying a group of subjects with disease and second group without
  • Frequency of exposure is determined in both groups
  • If more cases are exposed than controls this is an indication of exposure being risk factor
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15
Q

Describe the preferences between cohort studies and case-control studies

A
  • Cohort study thought to be better approach
  • More time consuming and costly
  • Unsuitable for rare diseases
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16
Q

What is the usual relationship between cohort and case-control studies?

A

Cohort studies are often performed to confirm interesting findings from case-control studies

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17
Q

What study is used to establish the efficacy of new treatments?

A

Randomised controlled trials

18
Q

What is a trial?

A

Any study conducted on patients to compared two or more treatments

19
Q

Describe a controlled trial

A

Contains a treatment which is included as a basis for comparison which can either be active or placebo

20
Q

What is randomisation?

A

Allocation of treatments to patients using some random process such as the toss of a coin or a computer generated number

21
Q

What is the main advantage of randomisation?

A

Produce study groups which are comparable with respect to both known and unknown factors which could influence the outcome

22
Q

What is block randomisation?

A
  • Commonly used in the two treatment situations where sample sizes for both treatments must be equal
  • Recruits patients in small blocks ensuring half patients within each block are allocated each treatment
  • Within each block order treatment allocation is random
23
Q

What is straitification?

A
  • Stratify patients into subgroups defined by important prognostic variables
  • Carry out restricted randomisation within each subgroup
24
Q

Why is allocation concealment necessary?

A

The decision to enrol a patient in a study could be influences by the knowledge of which treatment the patient may receive

25
Q

What is blinding?

A

Ensuring the assessor does not know which treatment the subject is receiving as the assessment of response may be influenced in knowledge of which treatment the patient has received is available

26
Q

What is double blind?

A

When the subject does not know the treatment and blind assessment is used

27
Q

What is single blind?

A

When either the subject or assessor is aware of the treatment used but the other is not

28
Q

What is the function of placebo treatments?

A

Help maintain blindness in some trials

29
Q

What is the placebo effect?

A

The knowledge that a participant is being treated may alter their response to treatment particularly when dealing with subjective outcomes e.g. pain

30
Q

What is an intention to treat principle?

A

Patients should be analysed as if they took the treatment regardless of whether they actually did or not

31
Q

What occurs if a randomised controlled trial is not of sufficient size?

A

It may be combined with others in a systematic review or meta analysis

32
Q

How are RCT with binary outcomes analysed?

A

2 x 2 frequency table

33
Q

What is risk ratio?

A

Risk of disease in the exposed group relative to risk of disease in unexposed group

34
Q

What is risk reduction?

A

Difference in risk between the two treatment groups

35
Q

What is the reciprocal to risk reduction?

A

Number needed to treat

36
Q

What is the number needed to treat?

A

Number of patients who need to be treated to prevent one end point

37
Q

What is odds ratio?

A
  • Odds on disease in the exposed group relative to the odds on disease in the unexpected group
  • i.e. odds of failure in treatment group A relative to odds on failure in treatment group B
38
Q

What is a more sophisticated method of odds ratio?

A

Logistic regression analysis

39
Q

Describe the data of a cohort study with regards to that of a randomised trial

A
  • Similar data collected
  • Exposure status taking the role of treatment in clinical trial and disease status taking role of outcome
  • Same summary measures used
40
Q

What is the key difference between case-control studies and cohort studies?

A
  • Cohort studies samples exposed and unexposed individuals and follow up for disease
  • Case control study samples diseased and non-diseased individuals and exposures are determined
41
Q

How are the findings of a case-control study summarised?

A

An estimation of odds ratio

DEN2025 - Dental Public Health and Behavioural Science (25 decks)

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