RESPONSE RATES TO RANDOM DIGIT DIALING FOR RECRUITING PARTICIPANTS TOAN ONSITE HEALTH STUDY

Objective. To evaluate the response rates when random digit dialing wa s used as a substitute for geographic area sampling and household inte rviews to recruit 2100 African Americans for a blood pressure measurem ent and hypertension-related knowledge and attitudes survey. Methods. Random digit dialing was used to identify African American adults livi ng in 12 low-income ZIP code areas of Houston, Texas. A brief survey o f hypertension awareness and treatment was administered to ail respond ents. Those who self-identified as African American were invited to a community location for blood pressure measurement and an extended pers onal interview. An incentive of $10 was offered for the completed clin ic visit A substudy of nonrespondents was carried out to test the effe ctiveness of a $25 incentive in increasing the response rate. Data fro m the initial random telephone interview were used to identify differe nces between those who did and did not attend the measurement session. Results. Ninety-four percent of eligible persons contacted completed the telephone survey, and 65% agreed to visit a central community site for blood pressure measurement. in spite of the financial incentive a nd multiple attempts to reschedule missed appointments, only 26% of th e 65% who agreed to attend completed the scheduled visit in the substu dy of the higher financial incentive, all of those who missed the orig inal appointment agreed to another appointment, and 85% of this subgro up kept it. Not being employed hull-time and a history of hypertension were consistently associated with agreement to be measured and keepin g an appointment In spite of the low response rate for scheduled appoi ntments, differences-other than in employment status and a history of hypertension-between responders and nonresponders were small and consi stent with what is usually observed in health surveys. Conclusions. Th e use of random digit dialing as a substitute for area sampling and ho usehold screening resulted in unacceptably low response rates in the s tudy population and should not be undertaken without further research on ways to increase response rates.