Contents
What is a priori subgroup analysis?
An a priori subgroup analysis is one that is planned and documented before examination of data, preferably in the study protocol, and ideally includes a hypothesized direction of effect. Subgroup treatment effect interactions identified post hoc must be interpreted with caution.
What is post hoc subgroup analysis?
Subgroup analysis is often divided into two types: pre-specified analysis and post hoc analysis. Pre-specified analysis is subgroup analysis that was planned during the initial experiment design stage, before looking at any data. Post hoc analysis is decided on and planned after the data has come in.
Is a subgroup of symbol?
We use the notation H ≤ G to indicate that H is a subgroup of G. Also, if H is a proper subgroup then it is denoted by H < G . Note: G is a subgroup of itself and {e} is also subgroup of G, these are called trivial subgroup.
Why is post hoc analysis bad?
Post hoc power analysis identifies population-level parameters with sample-specific statistics and makes no conceptual sense. Analytically, such analysis can yield quite different power estimates that are difficult and can be misleading.
How often are subgroup analyses used in clinical trials?
According to Pocock et al. [ 1 ], 70 % (35/50) of reported trials contained subgroup analyses, of which 60 % (21/35) claimed subgroup differences. The total number of reported subgroup analyses per published trial varied from one to 24 with a median of four. In 20 % of the trials, subgroup analyses were purely descriptive.
Are there problems in the reporting of subgroup analyses?
Problems in the reporting of subgroup analyses are not new. 1-6,18 Assmann et al. 2 reported shortcomings of subgroup analyses in a review of the results of 50 trials published in 1997 in four leading medical journals.
How many subgroup analyses were prespecified or post hoc?
In 40 trials (68%), it was unclear whether any of the subgroup analyses were prespecified or post hoc, and in 3 others (5%) it was unclear whether some were prespecified or post hoc.
When to present subgroup results in the abstract?
Present subgroup results in the Abstract only if the subgroup analyses were based on a primary study outcome, if they were prespecified, and if they were interpreted in light of the totality of prespecified subgroup analyses undertaken.