[Mark]

Lots of good points here. I do think that retention is a function of research site operation. Those I trust say the key word is relationships. This comes down to valuing people as people, not just as research “subjects” (I prefer the term participant.) This can look different in different places but comes down to a lot of common sense things like making participation easy and stress free, being as flexible as possible, demonstrating genuine concern for participants, and thanking them repeatedly. One thing I think our site has found successful is not having a hard line between recruiting staff and study staff. An effort is made to allow participants to maintain a personal relationship with the recruiters, even though they are not performing study functions.