TOPRANK Flashcards
people w/ condition are compred to people without
Case Control / Trohoc studies
feature
occurred before the start of the study
study proceeds backwars from effect to cause
uses a control or comparison group to support or refute an influence
Case control study- retrospective
advantages of cae contrl study
easy to carry out
rapid & inexpensive
few subj. are required
rare disease can be studied
no risk
disadv. case control study
Problem of bias
selection of appropriate control group
incidence cannot bw measured
no distinction between causes & associated fx
not suited to the evaluation of therapy
incidence can be calculated
several possible outcomes can be studied
direct estimate of relative risk is possible
dose
bias can be minimized
Cohort study adv.
involves large # of study projects
longer time neede to complete the study
attrition problem among the study population
selection of group is a limitig fx
diagnostic criteria can change over prolonged follow up
extensive record keeping is needed
study is expensive
Cohort Study disadvantages
tests new preventive & therapeutic agents
Experimental Epidemiology Intervention studies
Types of Experimental Epidemiology
Randomized controlled trials
Non-randomized or non-experimental trials
Randomized controlled trials types
- Clinical trials
- Preventive trials
- Risk- factor trials
conxerned w/ evaluating therapeutic agents
Clinical trials
trials of primary preventive measures
Preventive trials
interrupt the usual sequence in the development of disease for those individuals who have “risk fx” for developing the disease
Risk- factor trial
types of non-randomized trials
- Uncontrolled trials
- Natural experiments
- Before & after comparison- most common
to study the natural history of disease & natural outcome
identifyinng risk fx of the disease
finding out incidence rate
Limitations
Longitudinal
^Difficult to organize
*****Time consuming
forward looking study
collect information on an exposure of interest & compare eventual outcomes
Adv.
Prospective Study
relationship between the exposure & disease of interest
does not rely kn a history to determine past exposure
exposure is determined by past exposure records
Retrospective Study
study of group comparison based on epidemiologic principles
designed to test hypothesis that a particular agent procedure fsvorable alter the natural history of the disease
Experimental Study Design/ Field Trial / Clinical Trial
material or formulation like the test priduct without the active ingredient used in the control group
Placebo
Bias in Case control study
- Memory /recall
2.Selectionbias
3.Interviewer’sbias
4.Berkesonian bias
occurs when the group actually studied does not reflect the same distribution characteristics
Selection Bias
if the rate of disease is diff. among those lost to follow-up then internal validity of the study may be affected & relationship between exposure & out come may be changed
Follow- Up Bias
researcher know
participant - don’t know
Single Blind Trial
commonly used blinding
Double Blind
Triple Blind trial
Px
Researcher
Statistician
