Are there any variants of Randomized Controlled Trial? Could anyone suggest me some literature?
My answer is somewhat different:
1) Controlled clinical trials indeed do have a control group, but this is not the very reason for this terminology. Case-Control Studies do also have a control group, but are not called "controlled trials".
2) The difference between a laboratory study and a field study is constituted by the degree of standardization of the environment, but this is also not an essential for the terminology of "controlled trial".
3) The very reason of calling a randomized trial a "controlled" trial is using randomized treatment assignment in order to balance ("control") the impact of all other causal mechanisms (even those not known before starting the study) and therefore enabling a causal interpretation of any resulting differences of the outcome variable.
4) Randomization is the preferable technique to control for counfounding factors, but there might be other techniques, e.g. for ethical reasons.
A classical source to further clarifying this notion:
Campbell, D. T. & Stanley, J. C. (1966).Experimental and quasi-experimental designs
for research. Chicago: McNally.
It means that they have a Control group without the intervention being studied. It can be placebo, or another intervention. I think the best books for learning Clinical Epidemiology are:
1.- Clinical Epidemiology - A Basic Science for Clinical Medicind Paperback – January 1, 1991
by David L. Sackett, R. Brian Haynes, Gordon H. Guyatt
2.- Clinical Epidemiology
Robert Fletcher MD MSc, Suzanne W. Fletcher MD MSc
I recomend this article
Recommendations for conducting controlled clinical studies of dental restorative materials.
Hickel R, Roulet JF, Bayne S, Heintze SD, Mjör IA, Peters M, Rousson V, Randall R, Schmalz G, Tyas M, Vanherle G.
Clin Oral Investig. 2007 Mar;11(1):5-33. Epub 2007 Jan 30.
Its very good!
My answer is somewhat different:
1) Controlled clinical trials indeed do have a control group, but this is not the very reason for this terminology. Case-Control Studies do also have a control group, but are not called "controlled trials".
2) The difference between a laboratory study and a field study is constituted by the degree of standardization of the environment, but this is also not an essential for the terminology of "controlled trial".
3) The very reason of calling a randomized trial a "controlled" trial is using randomized treatment assignment in order to balance ("control") the impact of all other causal mechanisms (even those not known before starting the study) and therefore enabling a causal interpretation of any resulting differences of the outcome variable.
4) Randomization is the preferable technique to control for counfounding factors, but there might be other techniques, e.g. for ethical reasons.
A classical source to further clarifying this notion:
Campbell, D. T. & Stanley, J. C. (1966).Experimental and quasi-experimental designs
for research. Chicago: McNally.
Ulrich Frick
I liked the logic behind your explanation.
I will try to get the article which you have quoted.
I agree so much with Ulrich Frick his answer was very simple and didatic.
in relation to literature to learn a little more I also recommend Clinical Epidemiology
Robert Fletcher MD MSc, Suzanne W. Fletcher MD MSc as has done Stefan Danilla. It is maybe the easiest book to beginners
In the end, it relates to randomization. Randomization tends to produce study groups comparable with respect to known and unknown risk factors, removes investigator bias in the allocation of participants and guarantees that statistical tests will have valid significance levels.
Still there are researchers who argue that the word Controlled in RCT denotes the controlled environment.
Non-randomized clinical trial is a clinical trial and is very similar to RCT except for the randomized allocation. However it does not have the same strength as that of a RCT. The control rest and control groups may vary. I conducted one study that way.
It means a control group as a counterfactual.
Baseline control
Historical control
and concurrent control group.
The word controlled in RCT refer to control arm of the trial. RCT can calssified into 2 categories: clinical trials and community trials. In clinical trials we allocate the intervention at individual level (sample of patients in therapeutic trials or healthy persons in preventive trials) while in community trials intervention is introduced at level of the community (for example, if the researcher want to study the efficacy of adding iron to the flour in reducing level of anemia in the community, he/she adds iron to the flour used for making public bread in a community and leave another community uses bread without adding iron to flour.
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