Zelen's design is an
experimental design
The design of experiments (DOE, DOX, or experimental design) is the design of any task that aims to describe and explain the variation of information under conditions that are hypothesized to reflect the variation. The term is generally associ ...
for
randomized clinical trials proposed by
Harvard School of Public Health statistician
A statistician is a person who works with theoretical or applied statistics. The profession exists in both the private and public sectors.
It is common to combine statistical knowledge with expertise in other subjects, and statisticians may wor ...
Marvin Zelen
Marvin Zelen (June 21, 1927 – November 15, 2014) was Professor Emeritus of Biostatistics in the Department of Biostatistics at the Harvard T.H. Chan School of Public Health (HSPH), and Lemuel Shattuck Research Professor of Statistical Science ...
(1927-2014). In this design, patients are randomized to either the treatment or
control group
In the design of experiments, hypotheses are applied to experimental units in a treatment group.
In comparative experiments, members of a control group receive a standard treatment, a placebo, or no treatment at all. There may be more than one t ...
before giving
informed consent
Informed consent is a principle in medical ethics and medical law, that a patient must have sufficient information and understanding before making decisions about their medical care. Pertinent information may include risks and benefits of treatm ...
. Because the group to which a given patient is assigned is known, consent can be sought conditionally.
Overview
In this design, those patients receiving standard care need not be consented for participation in the study other than possibly for privacy issues. On the other hand, those patients randomized to the experimental group are consented as usual, except that they are consenting to the certainty of receiving the experimental treatment only; alternatively these patients can decline and receive the standard treatment instead.
In comparison, the current predominant design is for consent to be solicited prior to randomization. That is, eligible patients are asked if they would agree to participate in the clinical trial as a whole. This entails agreeing to receiving the experimental treatment as a possibility, receiving the control treatment as a possibility, and the uncertainty involved in not knowing.
Statistical and epidemiological issues
There are a number of advantages conferred by the post-randomization consent design.
*Clinicians are more comfortable with this design because each time consent is only sought for one treatment without the uncertainty of randomization.
*Patients correspondingly are not subjected to the uncomfortable feeling that they may or may not be receiving the experimental treatment. This means effects such as
resentful demoralization
Resentful demoralization is an issue in controlled experiments in which those in the control group become resentful of not receiving the experimental treatment. Alternatively, the experimental group could be resentful of the control group, if the ...
will not become an issue. Analogously, since patients allocated to the standard care group are not necessarily aware of the existence of an alternative treatment,
Hawthorne effect is also less of an issue.
Some disadvantages include:
*Contamination by crossing over may be more likely since patients assigned to the treatment group are fully aware of their assignment. Notably, statistical analysis should be performed with intention-to-treat.
*Lack of allocation concealment, which may produce further bias.
*Ethical drawbacks. Palmer (2002) notes, "in the few trials where
elen randomizationwas employed it has been met with disapproval from participants and others, being deemed inappropriately deceptive and manipulative, at least in trials for serious or life-threatening conditions."
See also
*
Cluster randomised controlled trial
*
Marvin Zelen (biostatistician)
Marvin Zelen (June 21, 1927 – November 15, 2014) was Professor Emeritus of Biostatistics in the Department of Biostatistics at the Harvard T.H. Chan School of Public Health (HSPH), and Lemuel Shattuck Research Professor of Statistical Science ( ...
*
Randomized controlled trial
A randomized controlled trial (or randomized control trial; RCT) is a form of scientific experiment used to control factors not under direct experimental control. Examples of RCTs are clinical trials that compare the effects of drugs, surgical ...
*
Statistics
References
*
*
*{{Cite journal, issn = 0962-2802, volume = 11, issue = 5, pages = 381–402, last = Palmer, first = C. R., title = Ethics, data-dependent designs, and the strategy of clinical trials: time to start learning-as-we-go?, journal = Statistical Methods in Medical Research, date = 2002, pmid = 12357585, doi=10.1191/0962280202sm298ra, citeseerx = 10.1.1.128.9963, s2cid = 1818466
External links
Introduction to the Special Issue Dedicated to Marvin Zelen Lifetime Data Analysis, Issue Volume 10, Number 4 / December, 2004. DOI 10.1007/s10985-004-4769-7, Pages 321-323.
Design of experiments
Clinical research