Arpan Singh (University of Leeds) – Design and Analysis of Therapist-led trials

Abstract: Therapist-led trials are central to evaluating interventions in psychotherapy, physiotherapy, and rehabilitation. These are typically designed as individually randomised, parallel-group trials, where patients are assigned to interventions at enrollment. The primary aim is to estimate the effect of the intervention, defined as a specific therapy or procedure of interest.

A persistent methodological challenge in such trials is the confounding of therapist effects with intervention effects. One proposed solution is to randomise patients to therapists, but this introduces significant practical constraints, including therapist availability, capacity, and turnover. Neglecting these constraints during trial design can lead to inflated costs and biased estimates of intervention effects. In this talk, we shall explore key logistical challenges in therapist randomisation and present strategies to address them at both the design and analysis stages. In particular, different randomisation methods will be examined, along with their implications for trial structure, statistical inference, and operational feasibility.