Adaptive crossover designs for assessment of symptomatic treatments targeting behaviour in neurodegenerative disease: a phase 2 clinical trial of intranasal oxytocin for frontotemporal dementia (FOXY)

Table 2 Efficiencies in sample size of adaptive crossover trial compared with traditional and parallel trial designs

Study design	Sample size dose selection^a	Sample size POC efficacy	Total sample size	Power
Traditional parallel arm^b	62	44	106	0.86
Traditional crossover	54	44	106	0.86
Adaptive crossover	60	24	84	0.86

^aPower calculations performed using G*Power were based on an effect size from a minimum clinically significant difference of 2 points on the NPI apathy/indifference domain score (d = 0.7) and power of 0.80 to permit analysis for males and females, with effect size of 0.7 based on pilot study results of a 3-point difference (d_karr = 0.7) [11]. For comparison, sample sizes assuming a smaller effect size are shown for each design
^bTraditional trial design-based on factor design (analysis of covariance). Four groups (three dose schedules + placebo), df = 3, disease severity as covariate, with sample size doubled to permit separate analysis of males and females
Traditional crossover design comprised three groups, df = 2, disease severity as covariate, with sample size doubled to permit separate analysis of males and females

ISSN: 1758-9193