Experimental epidemiological studies - randomized control trials, field trials, community trials: design, conducting, applications.
Experimental studies:
involve an experimental active attempt to change a disease determinant of the progress of a disease
Randomized control trials:
At the outset of a randomized controlled trial the criteria for entry to the study sample must be specified (for example, in terms of age, sex, diagnosis, etc) —> subjects studied should be representative of the target population in whom it is hoped to apply the results
Steps:
- drawing up a protocol: specifies i.e.e aims & objectives of study, questions to be answered, criteria for selecting study & control group, size of sample, treatment to be applied
- selecting reference & experimental populations: reference population= population to which the findings of the trial are expected to be applied, experimental population= population that actually participates in experimental studies —> participant criteria: give informed consent, representative of population, be eligible for trial
- randomization: statistical procedure b which participants allocated in to study & control groups, attempt to eliminate bias & allow for comparability
- manipulation or intervention: manipulation creates an independent variable (i.e. drug) whose effect is determined by measurement of final outcome which constitutes dependent variable (incidence of disease, survival time)
- follow-up: examination of experimental & control group subjects
- assessment of outcome: positive results= benefits of experiment measurers, reduced incidence / severity of disease, negative outcome= side-effects & complications
Field trials:
in healthy population
often prophylactic
relies on natural challenge
for primary prevention
Community trials:
experimental unit is entire community, population of defined area, breed, sex, species, etc.
are (mostly preventive) experimental studies with whole communities (such as cities or states) as experimental units —> interventions are assigned to all members in each of a number of communities