Which treatment-as-usual characteristics need to reported? A narrative review of content and contextual treatment-as-usual characteristics Authors: Neza Javornik, Daniel Powell, Marion Campbell, Marijn de Bruin INTRODUCTION: Treatment-as-usual (TAU) is often used as comparator in behaviour change trials, but its characteristics are poorly described in published manuscripts (i.e., what was TAU in this trial)? This study set out to identify what TAU characteristics may be relevant to report in health behaviour change trials. METHODS: A narrative review was conducted using a systematic search approach. PsycINFO, MEDLINE and Web of Science were searched using terms for TAU (in title) and trial or review (in abstract or topic). Data were extracted qualitatively from relevant health and clinical psychology studies published since 1998. Studies had to assess contextual and content characteristics of treatment-as-usual, and their potential impact on outcomes. One coder extracted data on study identifier, methodology, results, and TAU intervention characteristics. RESULTS: Eligible studies (N=31) included qualitative and systematic reviews and trial studies. Content was characterised as type of treatment (n=8), adherence to guidelines (n=2) or treatment components (e.g. behaviour change techniques) (n=7). Contextual characteristics, namely provider (n=7), setting (n=4), tailoring (n=3), duration (n=1), and mode (n=1), were mapped onto reporting frameworks. Credibility of treatment (n=2), attention (n=2) and therapeutic alliance (n=3) were additionally identified as potentially important. Contextual and content characteristics were predictive of outcomes in 26/31 studies. DISCUSSION: Extracted content and contextual TAU characteristics could mostly be integrated within the existing reporting frameworks (e.g. CONSORT-SPI, TIDieR). Additional TAU characteristics (credibility of treatment, attention and therapeutic alliance) were also identified. The extracted characteristics will be used to form a basis for a Delphi expert consensus on TAU reporting.