Mass mailing and staff experience in a total recruitment program for a clinical trial: The SHEP experience

The Systolic Hypertension in the Elderly Program (SHEP) staff contacted 447 ,921 screenees, of whom 11,919 (2.7%) were originally eligible and 4,736 (1 .1%) maintained eligibility and were randomized. The total number of partic ipants enrolled at the 16 clinical centers ranged from 133 to 559. The low yield of screenees to randomizations resulted from the study design, not fr om low levels of agreement to participate, and required the employment of a variety of recruitment strategies in a prudent overall plan. SHEP was one of the first clinical trials to use mass mailing as a primary strategy of r ecruitment. The study used mailing lists from seven generic sources. More t han 3.4 million letters of invitation were mailed; they yielded an overall response rate of 4.3%. Motor vehicle and voter registration lists provided the greatest numbers of names. Mailings to members of health maintenance or ganizations (HMOs) and registrants of the Health Care Finance Administratio n (HCFA) provided the greatest response rates. Considerable variability in response rates existed among clinical centers using generically similar mai ling lists. Generally, the number of hours spent on recruitment showed a po sitive, but not statistically significant, association with randomization y ields. The recruitment yield was statistically significantly higher in clin ics with experienced recruitment coordinators than in clinics with inexperi enced ones (p = 0.0008). From these findings we conclude that mass mailing is an important strategy in an overall recruitment program, that the involv ement of experienced recruitment staff is important, and that although the total time spent by staff on recruitment may also improve results, it matte rs less than the staff's level of recruiting experience. Controlled Clin Tr ials 1999;20:133-148. (C) Elsevier Science Inc. 1999.