Our Aim is Efficacy So we are concerning about the extent to which an intervention does more good than harm when provided under ideal conditions. Explanatory Trials
Our Aim is Effectiveness So, we are speaking about the assessment of the adequacy of that intervention to do more good than harm in regular clinical practic. Pragmatic Trials
Our Aim is the Efficiency So we are interested in the measurement of the effect of the intervention in relation to the resources it consumes. Cost Benefit Studies
Experimental Trials The Investigator have a Control over who is exposed and who is not exposed to a particular risk factor / intervention. The study Design is essential criteria to provide valid conclusions. The use of control group should be Ethical specially if there is a placebo will be tried.
Group Comparative RCT Prospective Each subject is receiving one treatment modality only subject/independent Statistical methods are used to compare the groups
Cross Over Studies of RCT Prospective Each subject in the interest and the control group Receives all the Interventions, so subjects act as their own control.
Problems of the Cross-Over Design It is a controversial design as it is rarely informative. Time Consuming as there must be sufficient time elapsed between treatment A and treatment B. Possibility of confounding bias between the effect of the drug A and drug B as the effect of drug A may be still present when drug B started.
Non-Randomized Controlled Trials Prospective The Investigator distribute the subjects between both groups Without Randomization
Uncontrolled Clinical Trial Prospective This design is suitable almost only in estimation of drug side effects and toxicity levels
Cohort Studies Prospective The exposed group is followed up for pre determined period of time
Example Follow Up for Next 5 years
Cohort Studies (contd.) Follow up for predetermined Period
Cross-Sectional Studies Cross Section Time Prospective Retrospective
Example Lung Cancer in 2005 between Smokers and Non Smokers Year 2000 Year 2010
Example of Cross Sectional Studies(contd.)
Case Control Studies Retrospective Follow Up for predetermined Period