My study involves repeated measures to compare the effectiveness of two distinct drug formulations at reducing the volume of an abscess, measured at three time-points (one baseline and two follow-ups), with participants in 5 groups (two treatments, Two positive controls [or placebo] and one negative control).
In some individuals (in all groups studied, but mostly in control groups, especially in follow-ups), abscesses have been "ruptured" suddenly due to increasing volume and/or decreasing wall thickness. On the other hand, complete treatment occurs when the abscess volume reaches a conventional zero (and not necessarily "real zero").
The question is that for data analysis, for example by the ANCOVA-Change method, should the cases leading to the rupture be removed or kept? If these cases are to be kept in the study and categorization based on Outcome measures (due to concerns about reduced power of the analysis) should be avoided, what measures should be considered?