Retrospective and Observational Study Designs

Question 1

Clinical studies

Answer 1

Discovery an effect
Test a hypothesis
Based on statistics (probability)

Question 2

Introduction

Answer 2

Research questions
Construct a working hypothesis
Design experiments
Observe and record results
Interpret data

Question 3

Study Design is directly linked to:

Answer 3

Objectives of the study
Measurements to be taken
Interpretation of results
Application of results

Question 4

Common mistakes

Answer 4

Inefficient or incorrect designs
Too may or too few pts
Use incorrect procedures
Plan for too many response measurement

Question 5

Observational Retrospective

Answer 5

Case reports/studies
Case-control
Cohort
Cross-sectional
- Studies that begin in present and follow the subjects into the PAST

Question 6

Observational Prospective

Answer 6

Cohort
Cross-sectional
- Studies that begin in present and follow the subjects into the FUTURE

Question 7

Utility of Observational Studies

Answer 7

Health issues in large groups of people
Interventional studies are unethical
Extremely rare events or long lag-time between exposure and outcome
NO intervention
Compares outcomes/experiences

Question 8

Retrospective study

Answer 8

Hypothesis generating
Exploratory
Pilot in anticipation of a prospective study
- Clarify the study question and hypothesis
- Inform the design of the prospective study (size, etc)

Question 9

Define case study/series

Answer 9

A description of one or a series of interesting cases

Observation –> hypothesis

Question 10

Case study Pros

Answer 10

Readily available information

Fast

Question 11

Case Study Cons

Answer 11

Depedent on availability and accuracy of chart records
Subject to selection bias
Uncontrolled
Least robust

Question 12

Define bias

Answer 12

A type of systematic error

“Any tendency which prevents unprejudiced consideration of a question”

Question 13

Case Control

Answer 13

Begin with outcome and look back for features of those with and without outcome
- Hypothesize cause of disease and ID RK

Question 14

Case Control Pros

Answer 14

Fast and few
Lots of new information
Only feasible option

Question 15

Case Control Cons

Answer 15

Highly susceptible to bias
Data collected for other reasons
Separate sampling of cases and controls
Difficult to assess incidence or prevalence

Question 16

Define Cohort Study

Answer 16

Start with a population at risk

ID cohorts of interest - those with RF and without

Question 17

Cohort Study Utility and Limits

Answer 17

Assess incidence and ID potential cause/predictors
Subject to bias
Losses to followup
Expensive and long
Not useful in rare events

Question 18

Cross-Sectional Study

Answer 18

Measurements are made at one time point and no followup
Describe an outcome of interest and its distribution in the population of interest
PREVALENCE estimate
SNAPSHOT in time

Question 19

Define Serial Surveys

Answer 19

Series of cross-sectional studies performed at different time points
Subjects in each group are different (births, deaths, migration)

Question 20

Serial Surveys Pros

Answer 20

Fast
Inexpensive
Part of a cohort

Question 21

Serial Surveys Cons

Answer 21

Cannot establish cause-effect relationships

Not practical for rare events