While attending the clinic, the participant will be asked to complete the QbTest at some point during the diagnostic process. inhibitor purchase Participants will also be asked to complete baseline outcome measures (see measures section). Phase 2, Treatment: Patients who receive a clinic diagnosis of ADHD and are allocated by clinicians to receive ADHD

medication initiated within 3 months of their baseline assessment will be asked to complete a second QbTest (Qb2) 4–8 weeks after medication initiation. This timeframe was chosen to ensure that all participants can complete their second QbTest before the 6-month follow-up. All participants will stay in the trial for 6 months and will be asked to complete outcome measures at 3 and 6-month follow-up, regardless of their diagnosis or whether they receive medication. With the aim of promoting participant retention and completion

of follow-up measures, participants will be compensated for their time with a £15 high-street voucher if they remain in the trial until 6 months. Measures Blinded members of the research team (CLH, GMW, AZV,) will be fully trained in all trial assessments and responsible for monitoring the distribution, completion and collection of all outcome measures. Primary outcome The primary outcome is the number of consultations until a confirmed clinical diagnosis is reached, as recorded on a short pro-forma. The pro-forma will be completed by clinicians after each consultation with the young person and/or

family and documents information about appointment duration, diagnosis and medication/treatment. The pro-forma can be provided by contacting the corresponding author. Secondary outcomes The secondary outcomes obtained from the pro-forma are: Number of days and duration of visits (in minutes) until a confirmed diagnosis is reached. Clinical confidence in diagnostic decision. Clinicians will be required to rate the confidence of their decision on a 7-point Likert scale (Definitely ADHD-Definitely not ADHD). Stability in diagnosis. Clinicians will be required to re-rate their diagnostic decision and confidence at 6 months. Other measures Development and Well-being Assessment (DAWBA29): Entinostat The DAWBA is a semistructured, investigator-based diagnostic interview for child mental health problems, including ADHD, which includes the (Strengths and Difficulties Questionnaire; SDQ30) as an initial screen. The parent and teacher DAWBA will be completed to compare the accuracy of clinic diagnosis (in QbO and QbB arms of the trial) to that of an independent clinical consensus diagnosis made using the DAWBA. Two experienced clinicians, blind to allocation, will review the DAWBA and arrive at a clinical consensus diagnosis.