Investigating strategies to improve attendance at screening visits in a randomized trial

Background A common method of recruiting for randomized trials is to send letters to potentially eligible patients inviting them to a screening appointment. In 3 consecutive UK studies the proportion attending from those invited fell from 49% [1] in 1994-1997 and 42%[2] in 1998-2001 to 13% at the beginning of an ongoing study in 2007. Procedures were similar in the 3 trials except that in 2007 the Patient Information Leaflet (PIL) was enclosed with the invitation letter. In order to understand whether the contents and/or style of invitation would explain the declining trend, 2 separate randomized comparisons were undertaken during the recruitment for the ongoing study.