Interim analysis

Clinical trials are unique in that enrollment of patients is a continual process staggered in time. This means that if a treatment is particularly beneficial or harmful compared to the concurrent placebo group while the study is on-going, the investigators are ethically obliged to assess that difference using the data at hand and to make a deliberate consideration of terminating the study earlier than planned.

tatistical methods of interim analysis

The design of many clinical trials includes some strategy for early stopping if an interim analysis reveals large differences between treatment groups. In addition to saving time and resources, such a design feature can reduce study participants' exposure to the inferior treatment. However, when repeated significance testing on accumulating data is done, some adjustment of the usual hypothesis testing procedure must be made to maintain an overall significance level (Armitage, McPherson & Rowe, 1969; McPherson & Armitage, 1971). The methods described by Pocock (1977) and O'Brien & Fleming (1979), among others, are popular implementations of group sequential testing for clinical trials. Sometimes interim analyses are equally spaced in terms of calendar time or the information available from the data, but this assumption can be relaxed to allow for unplanned or unequally spaced analyses, It is a tool used for statistical purpose.

Regulatory issues

Practical issues