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BMS1042 Epidemiolody > Study Designs > Flashcards

Study Designs Flashcards

1
Q

What is the difference between experimental and observational study designs?

A

Experimental- exposure is assigned by investigator.

Observational- exposure not assigned

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2
Q

What type of studies are analytical and descriptive studies?

A

Observational

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3
Q

What is the difference between analytical and descriptive studies?

A

Analytical studies have a control/comparison group, while descriptve studies do not.

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4
Q

What are the advantages and disadvantages of observational studies?

A 
Advantages:
- used to generate hypotheses
- can be the first observation of a rare occurrence
Disadvantages:
- Lowest level of evidence
- No comparison group
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5
Q

What is a case study and when is it used?

A

Detailed report by a health professional of a single patient.
Used for adverse effects and rare events

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6
Q

What is a case series?

A 
Advantages:
- Identification of rare disease and exposures
- Generates hypotheses
Disadvantages
- Selection bias
- Confounders
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7
Q

What are ecological studies?

A

Observational descriptive studies of populations or groups (rather than individuals).
Compare disease frequencies between different populations and different times.

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8
Q

What are the advantages and disadvantages of ecological studies?

A

Advantages:
- Fast, cheap, easy
- Hypothesis generating
Disadvantages:
- Highly susceptible to bias and confounders.
- Only associations can be drawn and not causation
- May confuse characteristics of a group for characteristics of an individual.

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9
Q

What is a cross-sectional study?

A

Asses the exposure and outcome at the same time and the direction of the relationship cannot be determined.
Measures the presence/absence of a disease and prevalence of a disease.

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10
Q

What are the advantages and disadvantages of cross-sectional studies?

A 
Advantages:
- Cheap, easy
- Prevalence estimated
- Useful for understanding etiology 
- Hypothesis generating. 
Disadvantages:
- Cannot infer causation
- Snapshot only and so results depend on time frame.
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11
Q

What are case-control studies?

A

Retrospective study in which data on exposures is collected in one point in time and exposures are collected at a previous point in time.
Compares the occurrence of possible cause in cases and control.
Odds ratios are used.

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12
Q

What are the advantages and disadvantages of a case-control study?

A

Advantages:
- Good for rare and long outcomes/disease
- Cheap, fast (2-3 years), easy.
Limitations:
- Control selection
- Through elimination of confounders, exposures may be eliminated
- High probability of recall bias
- High probability of selection bias as disease is known to researcher
- Measurement error
- Cannot estimate the incidence.

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13
Q

What is a cohort study?

A

The incidence of an outcome between those exposed and not exposed to a risk factor during the study time.

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14
Q

On what basis are participants selected in a case-control study?

A

Base on the presence/absence of outcome.

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15
Q

On what basis are participants selected for a cohort study?

A

Based on exposure to a risk factor.

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16
Q

What are the advantages and disadvantages of cohort studies?

A

Advantages:

  • Identifies the natural history of the disorder
  • Identifies the temporal sequence between exposure and outcome
  • Good for rare exposures and common outcomes
  • Very rigorous experimental design.

Disadvantages:

  • Selection bias
  • Confounders arise from individual participant differences
  • Insufficient to study rare diseases
  • Loss to follow-up
  • Expensive and time-consuming.
17
Q

What are randomised control trials?

A

Subjects are randomly allocated to intervention/control group and the outcomes of the two treatments are compared.

18
Q

What does randomisation is and RCT aim to achieve?

A

The two groups being a similar and possible.

19
Q

What is a community trial?

A

RCT at a group, rather than individual level.

20
Q

What is a meta analysis?

A

Comparison of separate similar studies.

21
Q

Which study designs allow investigation of rare disease?

A

Ecological, case-control, case studies.

22
Q

Which study designs do not allow study of rare disease?

A

Cross-sectional and cohort.

23
Q

Which study design allows investigation of rare causes?

A

Cohort study design.

24
Q

Which study design allows testing of multiple outcomes from a single exposure?

A

Cohort

25
Q

Which study designs allow study of multiple exposures?

A

Case-control and cohort.

26
Q

Which study design allows assessment of a time relationship?

A

Cohort, RCT

27
Q

Which study designs allow direct measurement of incidence?

A

Cohort, RCT

28
Q

Which study design involves investigation of long, latent periods?

A

Case-control.

29
Q

What is a randomised control trial?

A

A prospective study in which participants have an equal chance of being part of the control or experimental group.

30
Q

Why does blinding occur in RCTs?

A

To avoid performance bias (placebo effect).

31
Q

What are the advantages of RCTs?

A
  • Lowest risk of all four biases and confounders
  • Demonstrates strong causal relationship
  • Measure multiple outcomes
  • Measure incidence
32
Q

What are the limitations of RCTs?

A
  • Expensive
  • Long follow-up periods
  • Ethical issues (deception when using placebos).
33
Q

What is a cross-over trial?

A

Perform a randomised control trial then, following a washout period, cross the two over swapping over the intervention.

34
Q

What are the advantages and disadvantages of a cross over RCT?

A 
Advantages:
- Increases sample size
- Eliminates individual participant differences
Disadvantages:
- Order effects.
35
Q

What is a N of 1 RCT?

A

A single case is the participant of the trial: trial, washout period, different trial

36
Q

What is a systematic review?

A

Overview of medical literature with reproducible objectives and methodology

BMS1042 Epidemiolody (7 decks)

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