LAUSR

OBJECTIVE The objective of this study was to develop and pilot a standard framework which could be used to assess risk of contamination in psychological therapy trials, at the protocol development stage. STUDY DESIGN AND SETTING We developed and piloted a risk of contamination framework on a sample of 100 psychological therapy trial protocols registered on the ISRCTN registry (www.isrctn.com). We assessed all protocols as being low- or high-risk via three possible sources of contamination; 1) participant in control arm, 2) participant in intervention arm, 3) therapist in intervention arm. RESULTS Overall, we found that the risk of contamination across all 3 sources was low for most studies (86/100 trial protocols; 86%). We identified 14 studies which had a potentially high risk for contamination. The majority of these (N=10) were identified as risk of contamination arising from a therapist in the intervention arm. CONCLUSION The risk of contamination framework we piloted in this study could be a helpful tool for researchers aiming to identify and manage risk of contamination in their trial protocol development. We found that the risk of contamination was relatively low in the psychological therapy trials we sampled for this study, as measured by our framework, and could usually be mitigated through reasonable adjustments to the study design.