Questions tagged [clinical-trials]

Clinical trials are studies designed to test the safety and efficacy of new clinical interventions such as drugs or medical devices.

Clinical trials are studies designed to test the safety and efficacy of new clinical interventions such as drugs or medical devices. Clinical trials differ from other aspects of medical research for three main reasons:

  • Statistical methodology: Clinical trials have strict design requirements to avoid the introduction of bias in evaluating a new intervention. Clinical trial design is a specialized subset of biostatistics and involves knowledge of design of experiments, power and sample size calculations, and various modeling techniques to control for confounding factors.

  • Regulation: Clinical trials are used by many regulatory agencies to determine whether or not a drug is safe for use in patient care. Because of the importance of clinical trials in licensing and regulating new drugs and medical devices, clinical trials are subject to strict regulatory requirements regarding recordkeeping and data storage.

  • Goals of research: Clinical trials are primarily concerned with safety and efficacy. Initial trials may simply investigate whether or not the drug is safe for use in humans, by using relatively healthy subjects. Subsequent trials look for efficacy - that the new drug gives results that are at least as good as the current gold standard during a clinical trial. Drug effectiveness - the ability of the drug to successfully treat illness in actual clinical practice - is not usually assessed in a clinical trial, which is focused strictly on the experimental design that compares the new intervention to an existing intervention.

Clinical trials questions should be tagged using this tag; the epidemiology tag should be used for other health-related research that are not clinical trials.

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Best practice when analysing pre-post treatment-control designs

Imagine the following common design: 100 participants are randomly allocated to either a treatment or a control group the dependent variable is numeric and measured pre- and post- treatment Three obvious options for analysing such data are: Test…
Jeromy Anglim
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Which statistical model is being used in the Pfizer study design for vaccine efficacy?

I know there's a similar question here: How to calculate 95% CI of vaccine with 90% efficacy? but it doesn't have an answer, at the moment. Also, my question is different: the other question asks how to compute VE, using functions from a R package.…
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How to construct a 95% confidence interval of the difference between medians?

My problem: parallel group randomized trial having a very right-skewed distribution of the primary outcome. I do not want to assume normality and use normal-based 95% CIs (i.e. using 1.96 X SE). I am comfortable expressing the measure of central…
pmgjones
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What's wrong with (some) pseudo-randomization

I came across a study in which patients, who were all over 50 years of age, were pseudo-randomized by birth year. If the birth year were an even number, usual care, if an odd number, intervention. It's easier to implement, it's harder to subvert…
Jeremy Miles
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Why is bias affected when a clinical trial is terminated at an early stage?

An interim analysis is an analysis of the data at one or more time points prior the official close of the study with the intention of, e.g., possibly terminating the study early. According to Piantadosi, S. (Clinical trials - a methodologic…
ocram
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What is the difference between effectiveness and efficacy in determining the benefit of therapy 'A' on condition 'B'?

The context of this question is within a health framework i.e. looking at one or more therapies in the treatment of a condition. It appears that even well respected researchers confuse the terms efficacy and effectiveness, using the terms…
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Where to find raw data about clinical trials?

I wish to use raw data about clinical trials for the end year examination of my master students. These data could deal with any kind of molecule as long as the trials were complete (Phase 1 to 4). Do you have an idea where to find such a free…
Xavier Labouze
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Overall type I error when repeatedly testing accumulating data

I have a question about group sequential methods. According to Wikipedia: In a randomized trial with two treatment groups, classical group sequential testing is used in the following manner: If n subjects in each group are available, an interim…
ocram
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Should AstraZeneca's results be discounted?

This question is in regard to AstraZeneca's phase 3 clinical trial on the effectiveness of their COVID-19 vaccine. Patients were randomized to a two dose treatment group compared to a two dose placebo group. But a large portion of the treatment…
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Good text on Clinical Trials?

I'm an undergraduate statistics student looking for a good treatment of clinical trials analysis. The text should cover the fundamentals of experimental design, blocking, power analysis, latin squares design, and cluster randomization designs, among…
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Does significance test make sense to compare randomised groups at baseline?

Many randomised controlled trial (RCT) papers report significance tests on baseline parameters just after/before randomisation to show that the groups are indeed similar. This is often part of a "baseline characteristics" table. However,…
even
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How to detect which one is the better study when they give you conflicting results?

You so often come across in the press various studies that conclude directionally opposite results. Those can be related to the testing of a new prescription drug or the merit of a specific nutrient or anything else for that matter. When two such…
Sympa
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"Pragmatic" trials: what are they?

On twitter, a trialist Stuart Nicholls critiqued a recently published study by saying: Further to the very interesting paper by Dal-Re they flag several examples that question usage of the term pragmatic. Can a phase 3, multisite, double-blind,…
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Objections to randomization

In Clinical trials - a methodologic perspective, Steven Piantadosi writes (ch.13, p. 334): In Chapter 2, I noted the objections to randomization by Abel and Koch (1997) and Urbach (1993), and indicated the worth of studying their concerns and…
user7064
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How to best respond to investigator who wants to study secondary outcome

I'm co-investigator on a clinical trial where the we are studying the effect of an intervention. The study is powered to detect a clinically meaningful change for some primary endpoint. My questions are around the planned secondary endpoints. There…
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