Clinical trials bias

A bias is a cause of statistical analysis errors related to the experimentation method.

Yes, we are making mistakes like everyone, but not as much, I promise ...

Attrition bias

They are due to differences between groups. They are linked to outputs test or treatment interruptions.

For example, we have 2 groups of 100 participants : group A is treated, group B received a placebo.

I know, there are numbers, but it won’t be complicated !

In group A there are 50 outputs due to treatment intolerance, and 50 improvements.

In group B, 0 output, 50 improvements, 50 stagnation.

If we do not analyse outputted patients, we have 100% improvement in Group A against 50% in group B.

However if we analyse all patients, we do not observe any difference.

I told you it wasn’t hard was it ?

Selection bias

It is due to a difference in the composition between the treated and control groups. This can influence the results of the study. Randomization is the only way to avoid selection bias.

Monitoring bias

It is related to differences in the support between the treated group and control group.

Quality criteria

There are several quality criteria for a clinical trial :

Ethics

An ethical criterion is essential in any clinical trial.

Volunteers participating in clinical studies must be informed of possible risks and give an "informed consent".

We warn you about what will happen to you, isn't it great ?

In France, the advice of a committee for the protection of persons is required.

Controlled study

A control group is needed to validate the effectiveness of a procedure. Indeed, if a study of a drug shows 90% healing, someone might dramatically early conclude the effectiveness of the treatment.

What a mistake!!

In fact, if in the control group (which is not treated), the cure rate is 100%, the conclusion will be reversed!

Smart, isn't it ?!

Randomized study

The distribution between the two groups must be done by drawing lots.

Blinded study

It is preferable the subject doesn’t know which group he is assigned to and which treatment he receives, for example, an active drug or placebo. That is called a single blind.

Yeah, that could be disturbing, but we’ve got something better just after :

When the investigator also doesn’t know which patient is in the control group and which group is in the other, it is called a double blind study. That’s the best !

Multi-centered study

A trial taking place simultaneously in several different locations allows the study of a larger number sample and a larger diversity in the population included.

Monitoring Committee and Monitoring

Or as we say in English, yes, you're everywhere ! Data Monitoring Committee (DMC) or Data Safety and Monitoring Board (DSMB).

It is a group of independent experts who monitor the data in terms of patient safety.