In clinical trials, if we analyze, it is the randomization that yields accurate scientific evidence. In other words it means that causal relation between intervention and outcome is result of randomization.
Randomization is a method of allocation of treatment in patients in a study at random. What this results in is that every patient/subject gets a chance of being allocated either in the treatment group, standard control or placebo. This prevents the chance of even predicting about which group is assigned with what study arm, thus eliminating any possible bias.
This concept was first introduced in 1948 during the tuberculosis study conducted on 55 patients in which, patients were randomized to study drug or standard medication. To quote from that paper published, ‘determination of whether a patient would be treated by streptomycin and bed rest (S case) or bed rest alone (C case), was made by reference to a statistical series based on random sampling numbers drawn up for each sex at each center by Professor Bradford Hill; the details of the series were unknown to any of the investigators or to the co-coordinator and were contained in a set of sealed envelopes each bearing on the outside only the name of the hospital and a number. After acceptance of a patient by the panel and before admission to the streptomycin centre, the appropriate numbered envelope was opened at the central office; the card inside told if the patient was to be an S or C cases, and this information was then given to the medical officer at the centre’. Dr Bradford Hill was later knighted for his contributions to science including the contribution of randomization.
In randomization the allocation can be in different forms, it may be equal allocation i.e. on 1:1 ratio or may be unequal as well. There benefits of each type of allocation, such as in case of unequal allocation, chances of enrolling a patient in the placebo arm fall steeply, however the study will have loss of power.
Randomization is mainly of three types – Simple, Stratified and blocked. There are numerous other types but these three types are the most commonly used. IVR Systems are commonly used by pharmaceutical and contract research companies to carry out patient randomization.