Randomization Processes

Randomization Processes are one of the key aspects of any clinical trial.

Processes
There are mainly two processes involved. First is choosing a randomization procedure to generate a random and unpredictable sequence of allocations. This can be simply distributing the patients to any group in random order . There are a couple of statistical issues to consider in generating the randomization sequences:

Balance: since most statistical tests are most powerful when the groups being compared have equal sizes, it is desirable for the randomization procedure to generate similarly-sized groups.

Selection Bias: depending on the amount of structure in the randomization procedure, investigators may be able to infer the next group assignment by guessing which of the groups has been assigned the least up to that point. This breaks allocation concealment and can lead to bias in the selection of patients for enrollment in the study.

Accidental bias: if important co-variables or the variables existing with the main variables that are related to the outcome are ignored in the statistical analysis, estimates arising from that analysis may be biased.

A second and more practical issue is allocation concealment, which means not to reveal the group assignments to the investigators unless their allocation to their specific group has been ensured.

Unlike to this, impartiality is very difficult to maintain and study investigators also agree on this. But if the allocation concealment in randomized controlled trials is breached it creates more problems because randomization is introduced to minimize these kind of biases. So, for a clinical trial to take place in the right manner the allocation concealment must be observed and reported in detail in the publication. Recent studies have pointed out the absence of concealment procedures in their publications and those who do not report are very unclear or unsure about the concealment procedures in the protocols.