Conducting qualitative research within Clinical Trials Units: avoiding potential pitfalls.

The value of using qualitative research within or alongside randomised controlled trials (RCTs) is becoming more widely accepted. Qualitative research may be conducted concurrently with pilot or full RCTs to understand the feasibility and acceptability of the interventions being tested, or to improve trial conduct. Clinical Trials Units (CTUs) in the United Kingdom (UK) manage large numbers of RCTs and, increasingly, manage the qualitative research or collaborate with qualitative researchers external to the CTU.