An illustrative statistical analysis of cutoff-based randomized clinical trials.
Cutoff-based randomized clinical trials (RCTs) are designed to balance ethical and scientific concerns. Patients scoring below a cutoff score on a baseline measure (i.e. the least severely ill) are assigned to the control-treated group, those scoring above a second cutoff score (i.e. the most severely ill) are assigned to the test-treated group, and those scoring within the interval (i.e. the moderately ill) are randomly assigned. This paper provides a formal illustration on the statistical analysis of cutoff-based RCTs using data from the Xanax Cross-National Collaborative Study. To overcome problems specific to cutoff-based designs, we generally recommend a backward elimination approach that tests interactions before main effects.
Cappelleri
J C
JC
New England Medical Center, Center for Health Services Research & Study Design, Boston, MA 02111.
Trochim
W M
WM
D006801:Humans; D015233:Models, Statistical; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D012107:Research Design